Hamas has chosen Yahya Sinwar, one of the architects of the deadly Oct. 7 attacks on Israel, to lead the militant group’s political wing, it announced on Tuesday, consolidating his power over Hamas as it continues to fight Israel in the Gaza Strip.

Mr. Sinwar, the leader of Hamas in Gaza since 2017, has long been considered a planner of Hamas’s military strategy there. Now, he will also replace Ismail Haniyeh, the group’s previous political leader and a key liaison in the indirect cease-fire talks with Israel. Mr. Haniyeh, who had been living in Qatar, was killed in an explosion in Iran last week that has been widely attributed to Israel.

A hard-line figure born in Gaza, Mr. Sinwar, 61, is a prime target for Israeli forces and is widely believed to be hiding out in tunnels underneath the enclave to avoid Israeli attack. Despite that, he is thought to have been dictating the group’s position in the cease-fire talks.

His selection to lead the group’s political office comes as the Middle East braces for Iran and its proxies, including Hamas, Hezbollah in Lebanon and the Houthis in Yemen, to strike Israel in response to the killings last week of Mr. Haniyeh and a senior Hezbollah commander, Fuad Shukr.

Hamas and Iran have blamed Israel for planting the bomb that killed Mr. Haniyeh in the Iranian capital, Tehran, after he attended the inauguration of the country’s new president. Israel has declined to comment on Mr. Haniyeh’s death, but U.S. officials have privately assessed that Israel was behind it.

The supreme leader of Iran, Ayatollah Ali Khamenei, has promised to respond with a “harsh punishment.” And Prime Minister Benjamin Netanyahu of Israel has said that his country will “exact a heavy price for any act of aggression against us, from whatever quarter.”

Amid frenzied diplomatic efforts to prevent the violence from mushrooming into a wider regional war, the United States has ordered additional combat aircraft and warships that can intercept missiles, rockets and drones, to the Middle East.

For years, the leaders of Hamas’s political wing have usually been based outside Gaza or in the Israeli-occupied West Bank, creating a split power structure; from 2007 until the war began last year, Hamas governed Gaza, and its military strength has been concentrated there.

Mr. Sinwar’s selection to succeed Mr. Haniyeh seems to bridge that divide, but in precarious fashion; it appears unlikely that he could leave Gaza, as the Israeli military continues to hunt for him. In February, Israel’s chief military spokesman, Rear Adm. Daniel Hagari, said, “The hunt for Sinwar will not stop until we catch him, dead or alive.”

Born in the southern Gaza city of Khan Younis, Mr. Sinwar joined Hamas in the 1980s. He was later imprisoned for murdering Palestinians accused of apostasy or collaborating with Israel, spending over two decades in an Israeli prison. He was freed in 2011, along with over 1,000 other Palestinian prisoners, in exchange for a single Israeli soldier held by Hamas.

In his role as Hamas’s leader in Gaza, Mr. Sinwar was in many ways already more internally influential than Mr. Haniyeh, his nominal boss. Mr. Haniyeh served as Hamas’s diplomatic face abroad, while Mr. Sinwar controlled operations on the ground and has had close ties with Hamas’s military wing, analysts said.

Earlier this week, the Israeli military confirmed that it had killed Muhammad Deif, the elusive commander of Hamas’s military wing, in an airstrike on the outskirts of Khan Younis last month.

Elevating Mr. Sinwar to leadership of the political operation “is a symbolic decision that shows that Hamas is with Sinwar’s line,” said Fouad Khuffash, a Palestinian political analyst close to Hamas. “It is more of an honorific than a practical matter: No one knows where he is, even Hamas.”

Osama Hamdan, a Hamas spokesman, said in an interview with Al Jazeera that Mr. Sinwar had been chosen unanimously and that he was “accepted by everyone in the movement.” He said it was too early to discuss how his selection would affect the cease-fire talks, but suggested that little would change.

“The negotiations were managed by the leadership, and Sinwar was always present,” Mr. Hamdan said.

Israel Katz, the Israeli foreign minister, said in a statement that Mr. Sinwar’s appointment was “yet another compelling reason to swiftly eliminate him and wipe this vile organization off the face of the earth.”

Mr. Sinwar has not spoken publicly since the Hamas-led Oct. 7 attacks prompted Israel’s devastating 10-month campaign in Gaza and led Hezbollah to launch its own attacks on northern Israel in solidarity with Hamas.

On Tuesday, Hezbollah’s leader, Hassan Nasrallah, said in a televised addressed that his group and Iran were “obliged to respond” to the killings of Mr. Shukr and Mr. Haniyeh, “whatever the consequences.”

“What is required is confrontation,” Mr. Nasrallah said in a speech commemorating Mr. Shukr, who was killed in Beirut’s southern suburbs. “Our response will come, God willing, and it will be strong.” He added, “The wait is part of the punishment.”

Just minutes before he spoke, fighter jets — presumably operated by the Israeli military — ripped through the skies above Beirut, breaking the sound barrier, rattling apartment buildings and sending residents running for cover. Mr. Nasrallah mocked the sonic booms, saying they demonstrated how petty Israel had become.

“Hezbollah will respond, Iran will respond, Yemen will respond, and the enemy waits,” he said.

Just hours before Mr. Nasrallah spoke, Hezbollah launched a stream of attack drones into northern Israel in response to an Israeli strike a day earlier that the Israeli military said had killed a Hezbollah field commander.

Seven people in Israel were wounded in the drone attacks, Israeli paramedics said. The Israeli military said some Israeli civilians had also been injured by an Israeli interceptor missile that missed its target.

Earlier on Tuesday, an Israeli airstrike in southern Lebanon killed five people, according to Lebanon’s Health Ministry; Israel said it had hit structures used by Hezbollah.

More than 150,000 people have already been forced from their homes on both sides of the Lebanese-Israeli border since Hezbollah and Israel began striking each other in October. Israeli officials have openly discussed the possibility of invading Lebanon to push Hezbollah away from the border, as it did in 2006, after the war in Gaza concludes.

Abdallah Bou Habib, the Lebanese foreign minister, said on Tuesday that Lebanese officials had sought to discuss an appropriate response with Hezbollah that would not prompt a wider war. But after Mr. Haniyeh was killed in Tehran, infuriating Iranian leaders, the decision was “bigger than Lebanon,” he said.

“We are working so that any response does not bring us to total war,” Mr. Bou Habib said at a news conference in Egypt. “That would not benefit any states, nor would it benefit Israel.”

Diplomats and analysts have warned that a miscalculation by any of the combatants could set off a wider regional war at a particularly tense moment for the Middle East.

In an effort to contain the tensions, President Biden spoke on Tuesday with Qatar’s emir, Sheikh Tamim bin Hamad Al-Thani, and with Egypt’s president, Abdel Fattah el-Sisi, according to Sean Savett, a spokesman for the U.S. National Security Council.

Mr. Biden discussed efforts to de-escalate regional tensions and to secure a deal to end the fighting in Gaza and to free the remaining hostages seized during the Oct. 7 attack, Mr. Savett said.

Egypt said that Mr. el-Sisi had also spoken to King Abdullah II of Jordan, and that both leaders had emphasized the need for calm and for an immediate cease-fire in Gaza.

Tensions have also been escalating in the West Bank, where Israeli forces have killed at least 12 Palestinians, including a 14-year-old boy, since Monday, according to the Palestinian Authority’s health officials.

The Israeli military said that its operations in the West Bank, including two airstrikes on the city of Jenin, have been aimed at “terrorists” and that several “wanted suspects” had been arrested.

The Palestine Red Crescent Society said Israeli forces had fired on their ambulances in Jenin, just days after one of the group’s volunteer paramedics was fatally shot during an Israeli raid in Nablus.

Hwaida Saad and Anushka Patil contributed reporting.

Thousands of police officers fanned out across Britain on Wednesday amid fears that protests planned by far-right groups would descend into fresh violence after days of anti-immigrant riots shocked the country. But by late evening, large anti-immigration protests had not materialized and only a handful of arrests had been made.

Instead, thousands of antiracism protesters gathered in cities across the country, including Bristol, Birmingham, Liverpool and London. Some of those demonstrations were close to places that had been identified as potential targets for rioters. And as the summer evening that many had feared could turn violent made way for the night, many expressed relief that the worries of wide-scale violence had not been realized.

More than a dozen towns and cities across Britain experienced violent unrest over the past week, fueled in part by far-right agitators and an online disinformation campaign intent on creating disorder after a deadly knife attack on a children’s dance class in northwestern England. Much of the misinformation after the attack in Southport claimed that the teenage suspect — who was born in Britain — was an asylum seeker.

The BBC has reported that the suspect’s parents were from Rwanda. The police have not disclosed a motive for the stabbing attack. Britain has very tight restrictions on what can be reported once a case is underway.

Last week, and over the weekend, rioters clashed with the police, set cars on fire and targeted mosques and hotels housing asylum seekers. Far-right groups had called for further protests on Wednesday night, with the BBC reporting that the police were monitoring at least 30 locations, including London.

With tensions running high, some 6,000 specialist public-order police officers were mobilized nationwide to respond to any disorder. The authorities in several cities and towns stepped up patrols and gave the police extended powers to arrest those they believed were intent on causing unrest, even before any riots started.

Among a small number of arrests reported on Wednesday night was one in Southampton where Hampshire police said they had detained a 40-year-old man from nearby Eastleigh, suspected of violent or threatening behavior. That incident took place after a small group of anti-immigration protesters gathered but were outnumbered by counterprotesters, and the police kept the two groups apart.

In Bristol, police said there was one arrest after a brick was thrown at a police vehicle and a bottle was thrown, but that demonstrations there had remained largely peaceful. In the southern city of Portsmouth, police officers dispersed a small group of anti-immigration protesters who had blocked a roadway in the city. And in Belfast, Northern Ireland, where there have been at least four nights of unrest, disorder continued and the police service said on Wednesday it would bring in additional officers.

A list circulating on messaging apps and social media showed more than 30 spots that might be targeted by anti-immigration protests. Many were businesses or charities that support asylum seekers and refugees; a number of them closed after the list circulated.

That list included Liverpool, where by late evening, the antiracism demonstration that crowded a street in the east of the city had taken on an almost joyous tone. Hundreds of people gathered on the street outside a charity that supports asylum seekers, which had been on the list. The charity, Asylum Link Merseyside, has been closed for days in anticipation of violence, and on Wednesday evening, the windows at the center were boarded up.

Many businesses in the area had also closed early, with parents describing being asked to pick up their children from a nearby child care center.

On Wednesday evening, people banged drums, chanted “Fascists out!” and held signs that read “Love Not Hate” as a helicopter circled overhead. There was a large police presence, but the anti-immigration crowd failed to materialize. Instead, the gathering was diverse, made up of locals who were surprised that their street had become the center of a demonstration, union groups and others who voiced condemnation of the recent violence in Britain.

“It’s a quiet place normally, this neighborhood, and I am not happy with the far right trying to come here,” said Terry O’Brien, 52, who has lived in Liverpool all his life. “We have never had a problem with immigrants here, and people are trying to come here and bring violence.”

In Walthamstow, an ethnically diverse neighborhood in northeast London, word of potential far-right demonstrations had ricocheted around neighborhood WhatsApp and Facebook discussion groups. Residents quickly organized plans for a counterprotest, and by late afternoon, many shops and cafes on the main street had shut early, with some real estate agencies having boarded up their windows and doors with plywood.

By late evening, there was no sign of anti-immigration demonstrations, but thousands of counterprotesters filled the main streets, carrying signs that read “Refugees welcome” and “smash the far right.”

Experts who monitor the far right said that the threats of violence had already caused trauma for many, even before any action began, with communities on edge for possible violence.

“Understandably, the wide circulation of this list has caused a great deal of distress, unease and fear,” said Joe Mulhall, the director of research for Hope Not Hate, an advocacy group in Britain that researches extremist organizations. “Indeed, this list has been compiled precisely to spread these emotions within Muslim and immigrant communities.”

A snap poll published on Wednesday by YouGov found that after the week of disorder, nearly half of Britons view right-wing extremists as a “big threat,” a 15 percentage point increase in six months.

But people who said they voted last month for Reform UK, the populist anti-immigration party led by Nigel Farage, were less likely than others to see right-wing extremists as a major threat: Just 18 percent said they did.

While a vast majority of people polled opposed the riots, 21 percent of Reform UK voters expressed support.

Prime Minister Keir Starmer warned late on Tuesday that anyone involved in the violence would face “the full force of the law,” noting that more than 400 people had been arrested since the violence began, including people who had taken part in the riots and committed crimes online, and around 100 charged.

“That should send a very powerful message,” he said, “to anybody involved, either directly or online, that you are likely to be dealt with within a week, and that nobody, nobody, should be involving themselves in this disorder.”

Much of the unrest over the last week was driven by disinformation on social media and by calls to action by far-right groups on messaging apps like Telegram.

On Wednesday, Telegram said its moderators were removing channels and posts containing calls to violence, which it says are forbidden under its terms of service. It said that not only were moderators monitoring public parts of the platform, but it was using A.I. tools and user reports “to ensure content that breaches Telegram’s terms is removed.”

Michael J. de la Merced, and Adam Satariano contributed reporting from London, and Amelia Nierenberg contributed reporting from Rotherham, England.

All government agencies and offices were closed Wednesday in Tehran, and in 13 provinces, including some along the western and eastern borders, hours for government offices were limited to 6 a.m. to 10 a.m.

Iran also issued a notice to civilian aviation, warning that “gunfire will take place” for several hours on Wednesday night and into Thursday over parts of the country.

As Iran prepares to follow through on its vow to “severely punish” Israel over the assassination of the Hamas leader Ismail Haniyeh in Tehran last week, it is raising war jitters among the public. Yet there were few, if any, signs on the streets of Tehran and other cities that a conflict may be looming.

The government said that the shutdown on Wednesday occurred merely because of extreme heat (the temperature in Tehran was expected to reach 108 on Wednesday) and that the closings of airspace were for military exercises.

But the explanations belie the statements from officials that, as the acting foreign minister, Ali Bagheri, told state media on Tuesday, “Iran’s response will be definitive and severe.”

While the time and scope of Iran’s response remain unclear — whether it will act alone or in coordination with regional militias like Hezbollah in Lebanon and the Houthis in Yemen — the disconnect between the escalating rhetoric and the nonchalance about preparing the public is striking.

“We are in the dark, clinging to news programs on satellite television to figure out what is happening because our officials are not telling us anything,” said Maliheh, 66, a retiree in Tehran. Like others interviewed by telephone for this article, she asked that her surname be withheld for fear of retribution by the authorities.

The government has not issued any directives about what citizens should do if Israel responds with counterstrikes: no temporary shelters; no air raid drills; no warnings to stock up on emergency supplies; and no contingency plans for hospitals in the event of a strike.

“The answer is nothing, zero,” said Ehsan, a 41-year-old business owner in Tehran, when asked if he had heard of any public safety instructions. “The people are an afterthought in our country.”

On social media and in interviews in several cities, Iranians said they were anxious and confused.

“The situation is beyond our tolerance,” said Parisa, 37, an artist in Tehran. “Many people who never wanted to leave the country are now thinking about immigration. Everyone is sad, aggressive and worried.”

But some others questioned whether the war chatter was justified, doubting that an Israeli counterstrike to whatever Iran decides to do would disrupt daily routines or critical services such as electricity and water.

Mostafa, 36, a computer engineer in Rasht in northwest Iran, criticized the government’s support for militant groups in the region, saying it placed Iran in Israel’s crosshairs. Still, Mostafa said, he did not believe an all-out war was coming. “It will be a remote war and in the form of destroying specific targets,” he said. “So I am not that worried.”

Others said they were already emotionally exhausted from months of tumultuous events, each enough on its own to unnerve a nation, including a terrorist attack claimed by ISIS that killed over 200 people; exchanges of missile strikes with neighboring countries; nearly going to the brink of war with the United States and Israel; and the death of the president and foreign minister in a helicopter crash.

In the past week, the already battered currency plunged anew against the dollar while the stock market tumbled.

“We are just sick and tired of waking up every day to news that someone died, something blew up, the price of the dollar went up, and recently we have to worry about going to war every few months,” said Behdad, 39, of Tehran, who said his import-export business was suffering as a result.

Domestic challenges have also roiled the nation.

A widely circulated video showing female police officers beating two teenage girls and dragging them into a van because they were not wearing the hijab has stirred outrage. Many Iranians are calling for the newly elected reformist president, Masoud Pezeshkian, to fulfill his campaign promise to women and end enforcement of the mandatory hijab. (The video was shot in late June, before the presidential election.)

Lone voices have emerged among political analysts cautioning against heading into a conflict that could quickly spin out of control. Ahmad Zeidabadi, a reformist, said in a post on Telegram that while Israeli analysts and journalists openly debated the various consequences of a confrontation with Iran, nobody in Iran dared offer a similar honest reckoning and risk assessment.

“If someone says just one word — ‘Be careful and be cautious, and don’t jump in the water recklessly’ — he would be ambushed and accused of supporting Zionism and being in cahoots with America,” Mr. Zeidabadi wrote.

Being an artistic swimmer at the Olympics takes a dancer’s grace, a gymnast’s flexibility, a deep-sea diver’s lung capacity — and a large packet of gelatin, dissolved in water and applied to the head like shellac.

“It can be a big stressor if bits of your hair start to fall out or your headpiece comes off,” the Canadian artistic swimmer Claire Scheffel said this week, explaining the pivotal role that solidified gelatin plays in the athletes’ elaborate hair and makeup routines. “We really need to keep it all in place.”

Artistic swimming is one of the flashiest, and oddest, sports at the Games — a sui generis mishmash of ballet, swimming and gymnastics set to dramatic music and performed with Cirque du Soleil-level theatricality by athletes wearing sparkly swimsuits and extreme facial expressions. It was admitted to the Olympics in 1984 under its original name, synchronized swimming.

Though it is a crowd-pleaser, it has continually had to make the case, at least to the general public, that it is even a sport at all. (The nadir in its quest for respect was probably that same year, when Martin Short and Harry Shearer played a pair of very bad synchronized swimmers, one of whom did not know how to swim, on “Saturday Night Live.” Don’t mention that skit to anyone in the sport; they’ll never speak to you again.)

If Ginger Rogers had to do everything Fred Astaire did but “backwards and in high heels,” then artistic swimmers have to do the sort of thing that gymnasts and acrobats do, but upside down while holding their breaths for up to two minutes at a time, often in sync with not just the music but also their teammates. One tiny slip can throw everything off. When their heads are underwater, the swimmers remain afloat by sculling with their arms; when their heads are in the air, they stay up by using a treading motion called the eggbeater. They’re not allowed to touch the bottom of the pool.

In 2017, seeking to broaden its appeal and add greater athleticism to the routines, the sport rebranded itself artistic swimming, put in place a stricter judging system that incorporated a degree-of-difficulty index, and introduced a third routine, acrobatics, alongside its familiar technical and free routines.

The sport is much harder than it used to be, in part because of its increasingly elaborate acrobatic lifts. The swimmers form platforms, or bases, with their bodies and elevate a teammate, known as a flyer, far above the water — whereupon the flyer might strike a pose like a standing split before leaping high into the air and flipping, twisting and the like back into the water. (Think cheerleading lifts, but in a pool.)

These are the first Olympics to admit men in the sport; each team is allowed to include up to two male swimmers. But while a generation of men is rising through the ranks and may be ready to compete by 2028, few have experience in team competitions. The result is that there are no men on any of the teams in Paris.

(The United States’ best male bet, the veteran artistic swimmer Bill May, 45, nearly made it to the Olympics but was left off the roster at the last minute. In an acknowledgment of his towering stature in the sport, May was introduced to the adoring crowd on Tuesday, opening the proceedings by rapping a staff three times on the deck next to the pool.)

The routines are hard enough. But the fact remained that even before entering the water for the technical program on Monday, Nuria Diosdado of Mexico spent a full two hours getting ready. That entailed gelatinizing her hair and corralling it into place along with an elaborate hairpiece; applying waterproof makeup vivid enough to be seen by judges halfway across the pool; and putting on a sparkly swimsuit that made her look like an aquatic drum majorette.

“It’s not enough to be good — you have to look perfect in your face, in your makeup, in your body,” Diosdado said after the Mexican routine, a rollicking homage to Freddie Mercury set to Queen’s “Don’t Stop Me Now.” “And you have to look happy the whole time, even when people are kicking you under the water. We might be smiling, but actually we’re acting.”

Theatricality and impression are part of the score, but the need to exude constant beaming delight — even when your teammate has made an egregious mistake or you have swallowed water, slipped out of sync or been kneed in the stomach — is a challenging element of the sport.

“It’s a weird dynamic, but, you know, we’ve been doing it our whole lives,” said Anita Alvarez, a member of the American team.

Consider the difference in demeanor between a marathon runner and an artistic swimmer.

“You see marathon runners at the end of the race, and they’re covered in pee and puke, and they’re barely able to cross the finish line,” Alvarez said. “But we have to make it all look effortless. Which, of course, it’s not.”

And while marathon runners are awarded foil blankets after a race and allowed to lie on the ground, groaning and clutching their hamstrings, artistic swimmers have to swim decorously to the side of the pool, breast-stroking in tandem with their teammates as if they were ladies at the club trying not to get their hair wet. Once poolside, they have to effect pleasant expressions and no sign of fatigue or pain while they wait for the score, no matter bad it is.

Every team at the Games performs three routines — technical, free and acrobatic — and each routine has its own theme and music. (The United States won silver in the team finals on Wednesday night, behind China; the duet competitions, made up of two athletes from each country, start on Friday.) The themes can depict narratives, as in Spain’s world-championship-winning routine set to Led Zeppelin’s “Stairway to Heaven” in 2009 — if you look closely, you might spot the bustle in the hedgerow. They can also be vaguer and broader, as in Japan’s free routine (theme: chess) on Tuesday.

Not surprisingly, water comes up a lot as a motif. Australia’s free routine on Tuesday was “Avatar,” meant to show how the swimmers feel “at one with the water,” the announcer explained. The United States went with “I Am Water,” with a high-concept soundtrack featuring narration by Jason Momoa — Aquaman himself — and a routine that evoked watery activities like melting, rippling, dripping, gurgling and, of course, splashing.

The theme for the Canadian team’s technical routine was “Forest Magicians.”

“We’re really trying to give the vibe of the forest, of the powers that are within it,” Scheffel said. “We’re trying to take energy from the sun and the moon and the solar system.”

The swimmers’ costumes were festooned with feathers. “I think they’re meant not to be a particular bird, but more of a general bird,” Scheffel said. “The feathers really capture the forest vibe.”

The sport’s main features — the difficulty of the routines and the emphasis on appearance and showmanship — work in constant tension with each other.

“I think it just adds to the sport,” Carolyn Rayna Buckle of Australia said. Her team performed a jungle-themed routine set to Hans Zimmer’s “Volcano,” from the 2008 film “Madagascar: Escape 2 Africa.” “Not only is it a very difficult sport, but I also get to perform and put on a show. And people love to watch synchronized swimming.”

After a competition, the athletes have to attend both to their tired bodies and to their hardened hair, now covered with a thick layer of rubbery gelatin. If you want to see what it takes to get it off, Daniella Ramirez of the United States has kindly posted a series of TikTok videos depicting this less-glamorous aspect of her sport.

Nearly four million people have already viewed Tuesday’s installment, which shows Ramirez painstakingly peeling stray pieces of gelatin from her head. “The Olympic peelies,” she calls it.

As he sat in a Russian jail for five months, the human rights champion Oleg Orlov sometimes grew wistful: What if he walked free someday as part of a deal between Russia and the West?

The chances that President Vladimir V. Putin would make a prisoner swap like that seemed as remote as a “star twinkling far, far, far away on the horizon,” Mr. Orlov, 71, said this week. The dire state of the relationship between Moscow and the West, and their diverging interests, appeared to rule out the kind of detailed negotiation necessary for such a complicated deal.

But last week, it happened, in the most far-reaching prisoner swap with Moscow since the Cold War: Mr. Putin and his ally Belarus freed Mr. Orlov and 15 other Russians, Germans and Americans in exchange for a convicted assassin and seven other Russians released by the West. It was a moment when Mr. Orlov saw anew how core Mr. Putin’s past with the K.G.B., the Soviet spy agency, was to the Russian president’s identity — and to the sort of country he’s trying to shape Russia into.

The swap happened because “Putin is a K.G.B. man, an F.S.B. man,” Mr. Orlov said in a phone interview four days after two private jets carrying him and other released prisoners landed in Cologne, Germany. Espionage is a subject Mr. Orlov knows well, having spent decades studying the crimes of the Soviet secret police as a co-founder of the Memorial human rights group, which was awarded the 2022 Nobel Peace Prize.

Mr. Putin served as a K.G.B. agent in Dresden, East Germany, in the 1980s and ran the F.S.B., its domestic intelligence successor agency, in the 1990s. To the Russian leader, Mr. Orlov said, showing loyalty to the F.S.B. and other Russian intelligence services by winning their agents’ freedom trumped the political risk of releasing opposition figures whom the Kremlin had branded as traitors.

Last Thursday’s seven-country exchange — and the heroes’ welcome the returning Russians received in Moscow, including a red-carpet greeting from Mr. Putin — exemplified the security-focused state that Mr. Putin has built. It also highlighted the deal-making side of his leadership style, a characteristic that appears to have remained intact despite the heightened tensions with the West from the war in Ukraine.

The top story on one of Russian state television’s prime time newscasts on Monday showed how central the K.G.B.’s legacy has become to the Kremlin’s messaging about patriotism and national identity. It was an exclusive interview with two of last week’s released spies: a couple dispatched to Slovenia by another of the Soviet spy agency’s modern-day successors, the S.V.R. foreign intelligence service.

Anna Dultseva and Artem Dultsev impersonated an Argentine couple so thoroughly in Slovenia that they spoke Spanish to their children at home. In the interview, Mr. Dultsev described in halting Russian — he had barely spoken the language in his years undercover — how a fellow S.V.R. agent visited him in a Slovenian jail and passed along greetings from Mr. Putin.

“He said that Vladimir Vladimirovich and the S.V.R. are doing everything possible for our release,” Mr. Dultsev recalled, referring to the Russian president formally by his patronymic.

Spies like the Dultsevs “give their whole life to serving the motherland and make sacrifices that a normal person wouldn’t understand,” the state television reporter said. “For instance, they raised their kids as Spanish-speaking Catholics. Now they’ll have to learn about borscht and our New Year.”

Dmitri S. Peskov, the Kremlin’s spokesman, claimed that the Dultsevs’ son and daughter, learned only on the plane to Moscow after Thursday’s swap that they were Russian. He also confirmed that Vadim Krasikov, who was convicted of killing a Chechen separatist fighter in a Berlin park in 2019 and released last week, was an employee of the F.S.B. domestic intelligence agency with personal links to Mr. Putin.

But beyond celebrating the purported patriotism and sacrifice made by Russia’s agents, there has been another element to the Kremlin’s messaging since last Thursday: good spycraft also means making deals with your adversary. Of course, in Mr. Putin’s Russia, such deals can be based on what many in the West see as tantamount to hostage-taking of people like Evan Gershkovich, the Wall Street Journal reporter released as part of last week’s deal.

“This was a very tough chess game, played according to the best textbooks, lasting a tediously long time,” Dmitri A. Medvedev, the deputy head of Mr. Putin’s security council and one of the most hawkish members of his retinue, wrote after the swap.

Western officials involved in the negotiations said the Kremlin insisted on running the talks not through diplomatic channels but between spy agencies. The C.I.A. led the negotiations for the United States, and Western officials say Mr. Putin largely relied on the F.S.B., the agency he appears to trust most, even though its domestic intelligence role makes it more of a counterpart to the F.B.I.

And while Western officials have described encounters with Russian diplomats in recent years as unproductive harangues, people involved in the secret negotiations with the F.S.B. leading up to last week’s swap said they were focused and professional. The Kremlin sounded a similar message.

“To be fair,” Mr. Medvedev wrote, “our ‘Western friends’ also displayed the necessary pragmatism and a tendency toward reasonable compromises at a certain moment.”

The eagerness on both sides to make a deal was reflected in its timing: months before an American election and the subsequent conclusion of President Biden’s term as president. A person close to the Kremlin who was involved in some of the discussions said the thinking in Moscow was to “strike while the iron is hot” and cinch a deal while there was one to be had. He spoke on the condition of anonymity because he wasn’t authorized to discuss the negotiations publicly.

Mr. Putin sees former President Donald J. Trump as a fickle force who is hard to negotiate with, some analysts who study the Kremlin say. And given Mr. Trump’s toxic relationship with Germany, the Kremlin may have doubted that he would be able to convince Berlin to give up Mr. Krasikov, the linchpin of the swap, Alexander Baunov, a senior fellow at the Carnegie Russia Eurasia Center, argued.

The interest in deal-making Mr. Putin displayed in the swap led some analysts to speculate that a similar approach of secret talks between spy agencies could also bring about a cease-fire in Ukraine. Indeed, even as their war has raged, Russia and Ukraine have repeatedly negotiated prisoner-of-war exchanges, including at least three swaps freeing 520 prisoners between May and July.

Western officials involved in the talks played down that possibility. Last week’s prisoner swap, they said, resulted from a rare overlap in interests among Washington, Berlin and Moscow. When it comes to Ukraine, they said, the two sides remain much further apart.

But people involved in the talks did not rule out future deals — at least to exchange more prisoners. Mr. Orlov, the human rights activist, said that he and other political prisoners freed last week had begun strategizing about how to get more of their comrades released before they even landed in Germany.

Ilya Yashin, a prominent opposition politician whom Mr. Putin released, acknowledged in a YouTube broadcast on Sunday that engaging with Mr. Putin in prisoner exchange talks could only motivate him to take further hostile measures. But, he went on, there should be no illusions: No matter how the West behaves, Mr. Putin will not play by its rules.

“All dictators take hostages and torture them publicly, getting some advantage for themselves,” he said. “There is no way for opponents of dictators to act that would exclude this.”

For months, Erez Bergman had been working to encourage the evacuated residents of northern Israel, near the border with Lebanon, to return to their homes, with the hope that children could return to their schools this fall and residents could fix up the damage wrought by Hezbollah’s missiles and drones.

Like 80,000 other Israelis from the north, Mr. Bergman, 51, his wife, Maya, and their three school-age children left their house in Kibbutz Snir last October, after the Israeli government decided to distance residents from the northern border — the first such mass evacuation of the area in Israel’s history.

Following the Hamas-led Oct. 7 attacks and Israel’s bombardment of Gaza, Hezbollah was firing rockets into northern Israel and the Israeli military was hitting back, leading to months of tit-for-tat attacks that hit villages and towns in both southern Lebanon and northern Israel.

In April, the Bergmans decided to return to Snir, a cooperative village in the picturesque Galilee Panhandle, a finger of Israeli territory that juts upward along the border. But in late July they had to leave again — for how long this time, they don’t know — as tensions between Israel and Hezbollah reached their highest level in months. Mr. Bergman and other northern residents now say they feel as if they may be looking at “another lost year.”

Before the latest escalation in violence, Mr. Bergman had been spearheading a “Coming Home” project on behalf of the local council with the aim of bringing as many of the evacuees as possible back for the start of the new school year on Sept. 1. He came back with his family “out of Zionism,” he said in mid-July, sitting at the family’s dining table with a panoramic view of southern Lebanon.

He was hoping to revive his largely abandoned community and others in the area, which have long embodied Israeli sovereignty and resilience.

Or to put it more plainly, he said, “We were fed up being in hotels.”

Mr. Bergman, speaking after a night of heavy barrages, said the family was already having misgivings about their decision to return home.

Days later, a missile landed at the bottom of the Bergmans’ back yard, blowing out all the windows and causing damage inside the house. Luckily, nobody was home at the time.

Half of Snir is in the direct lines of sight of Hezbollah strongholds in south Lebanon, leaving it exposed. Between the booms, an eerie silence prevailed. Snir’s clinic and grocery store were not functioning. Mr. Bergman said it was “like living in a graveyard.”

The family was not able to sit out on their back terrace and were living in a permanent twilight, keeping the curtains and blinds closed.

On July 23, Israel’s education minister, Yoav Kish, announced that the risk was too great and that schools in the evacuated zone, within three miles of the border, would not reopen next month.

Then, on July 27, a rocket from Lebanon killed 12 children in the Druze Arab village of Majdal Shams in the Israeli-controlled Golan Heights. Israel subsequently assassinated Fuad Shukr, a senior Hezbollah commander, in Beirut. And the leader of Hezbollah, Hassan Nasrallah, threatened retaliation for Mr. Shukr’s killing, fueling fears in both Israel and Lebanon that the cross-border hostilities could spiral into all-out war.

About a week ago, the Bergmans left again, going to stay in Kibbutz Beit Alfa, 70 miles to the south. Speaking later by phone, Mr. Bergman said they are now reconsidering their own future in Snir. They will see how things develop and wait out the coming storm, he said.

Communities like Snir were established decades ago by hardy pioneers who came to work the border lands and establish Israeli sovereignty up to the last inch of territory. Their fates are uncertain. Once government funding for temporary, alternative accommodations runs out, community leaders fear that those who do move back will be the financially weaker residents who have fewer options, and that many young families won’t return at all.

In the Galilee Panhandle, the summer months are usually filled with vacationers kayaking in the cool waters of the Jordan River and its tributaries. Many villages in the area offer holiday accommodation and would normally be earning good income from tourism.

This year, the hillsides, orchards and fields are a checkerboard of dry, scorched earth, a result of bush fires, mostly set off by Hezbollah’s frequent attacks.

This close to the border, there is practically no warning time for incoming fire. Typically, the sirens go off after the projectiles already have been intercepted or have struck. The residents hear the roar of the rocket engines and see the drones as they fly overhead. The Bergmans’ house has a fortified safe room, but many do not.

Since Oct. 7, at least 22 Israeli soldiers and a similar number of civilians have been killed by Hezbollah’s barrages from Lebanon. More than 460 people in Lebanon have been killed by Israeli fire. Most were militants, but more than 100 were civilians, including 12 children and 21 health workers, according to the United Nations and Lebanon’s Health Ministry.

Many of the Israelis left in the frontline communities belong to the armed local emergency teams, now serving under the auspices of the military reserves.

A member of Snir’s emergency team, Lior Shelef, 48, said in mid-July that he was the only person left on his street.

Born and raised in Snir, Mr. Shelef remembered sleeping in a bomb shelter for three years as a child, during Israel’s first war in Lebanon in the 1980s.

“We want to make sure that the children coming back here will have a better childhood,” he said, adding that while his own family, living in a hotel a half-hour’s drive south, was not about to return, “We will never give up our home.”

Some Israelis say they want to see military action that would permanently distance Hezbollah forces from the border. But like some others here, Mr. Shelef seemed ambivalent about the need for an all-out conflict with Hezbollah in Lebanon, which would probably be devastating for both countries. In the end, he said, quiet will be restored only by means of a diplomatic resolution “with a war or without a war.”

Kfar Szold, a kibbutz that has not been evacuated, is a few minutes’ drive from Snir. Many of its members left anyway, soon after Oct. 7. But they did not receive government funding for alternative accommodation, and gradually, many have returned.

Nitai Galili, 31, a naturopath and resident of Kfar Szold, spent six weeks in Portugal after Oct. 7 before coming home. The mother of a 1-year-old, she said she felt “a constant existential fear.”

One barrage of rockets recently hit the road outside the kibbutz, narrowly missing two cars.

“You can last it out for a month or so,” Asaf Langleben, 49, the chairman of Kfar Szold, said, “but there’s no end in sight.”

The biggest East-West prisoner exchange since the Cold War last week was hailed as a triumph by both Washington and Moscow. But it left the family and friends of a jailed Nobel Prize winner and other imprisoned opponents of President Aleksandr G. Lukashenko, the longtime dictator of Belarus, puzzled and bitterly disappointed.

Belarus was involved in the swap, releasing a German citizen who had been sentenced to death, but it freed none of its nearly 1,400 inmates classified as political prisoners by Viasna, a human rights organization, as Russia did.

“We are very saddened that not a single Belarusian was released,” said Alena Masliukova, an activist with Viasna. She added that “Belarus has more political prisoners than Russia: 1,400 in Belarus compared to 700 in Russia,” but unlike Russia has faced little sustained pressure to set its prisoners free.

That may be because Belarus, which has fewer than 10 million people and has been led since 1994 by Mr. Lukashenko, is widely viewed as an eccentric Russian puppet state and, despite a sustained reign of terror, commands little attention in its own right.

But the absence of Belarusian prisoners from last week’s sprawling exchange has raised questions about why opponents of Mr. Lukashenko abroad, led by Svetlana Tikhanovskaya, the self-styled national leader of Belarus, have failed to make the release of prisoners a priority for the United States and other Western governments.

That stands in stark contrast to Russia’s opposition movement in exile, which has campaigned vigorously to have Russian dissidents freed.

Ms. Tikhanovskaya’s office in Vilnius, the capital of Lithuania, sent a message to Western diplomats last week acknowledging that “there is a perception among part of the society and experts that we have not done enough to prioritize the issue of Belarusian political prisoners to ensure their inclusion” in the prisoner swap. That, it said, was not true.

Among those in prison in Belarus is Mr. Tikhanovskaya’s husband, Sergei Tikhanovsky.

Also left out of the prisoner swap was Ales Bialiatski, a founder of Viasna who was awarded the Nobel Peace Prize in 2022. He is serving a 10-year sentence in Belarus for his role in huge, nationwide street protests in 2020, which were triggered by public fury over Mr. Lukashenko’s claim that he had won a landslide victory — his sixth in a row — in a fraud-tainted election.

Mr. Bialiatski’s wife, Natalia Pinchuk, lives in Norway, which, as part of Thursday’s swap, released a Russian spy who had masqueraded as a Brazilian. She said it “was heartbreaking for me and for imprisoned Belarusians that none of them was released.” She added that she had had no idea a swap was being negotiated until it took place.

Poland, which, as part of the swap, released a Spanish-Russian journalist arrested in 2022 as a spy near the Polish Ukrainian border, also came away empty-handed. Mr. Lukashenko resisted Polish demands that he free Andrzej Poczobut, an ethnic Polish journalist and minority rights activist in Belarus who was sentenced last year to eight years on national security charges.

“Why is the release of Belarusian political prisoners not a priority for the West?” asked Tatiana Khomich, the sister of Maria Kolesnikova, who has become a symbol of resistance to Mr. Lukashenko. Ms. Kolesnikova helped lead the 2020 protests and, after being abducted by security forces, tore up her passport to avoid being bundled out of Belarus.

That act of brave defiance made her a hero for many Belarusians and, in the event of her eventual release from prison and forced exile in the West, a potential leader of the fractious opposition movement in exile and rival to Ms. Tikhanovskaya.

Ms. Tikhanovskaya, a presidential candidate in the disputed 2020 election, fled to Lithuania soon after declaring herself the victor in the vote. She has struggled in exile to dent the Belarusian leader’s brutal grip on power and his increasingly close alliance with and dependence on President Vladimir V. Putin of Russia.

Mr. Lukashenko has resisted sending Belarusian troops into Ukraine in support of Mr. Putin’s forces, but allowed his country to be used as a staging ground for Russia’s military and, with help from Russian security forces, has snuffed out internal dissent.

Ms. Tikhanovskaya’s supporters have claimed to have been behind attacks on a Russian warplane and railway lines inside Belarus, but these were nearly all actually carried out by Ukrainian security services. There is no evidence that the government-in-exile she leads has a significant following inside Belarus.

For some, the absence of Belarusian political prisoners from the swap highlighted the travails of an exile movement that has been supported with millions of dollars in Western aid but had trouble making its voice heard either inside Belarus or in Western capitals.

Ms. Tikhanovskaya lost her main advocate inside the U.S. government in 2022 when the tenure of Ambassador Julie Fisher, who had served since 2020 as the U.S. special envoy for Belarus, ended. Based in Vilnius herself, she had been a loud champion of the exiled Belarus opposition.

In an effort to rally support behind Ms. Tikhanovskaya, more than 200 exiled Belarusian activists gathered in Vilnius last week and declared her “national leader” until Belarus holds free and fair elections, or she steps aside.

That gathering did not include supporters of several jailed political leaders who are at odds with Ms. Tikhanovskaya. These include Viktor Babariko, a popular former banker who has been in jail since 2020 and, according to some analysts, would have the best chance of defeating Mr. Lukashenko in a free election. The Belarusian KGB security service arrested him shortly before the 2020 vote to prevent him from running.

Artyom Schraibman, a Belarusian political analyst now living in Warsaw, lamented that “Belarusian democratic forces” have been “engaging in diplomacy with the West regarding Belarus for many years but have not managed to establish political prisoners as a priority issue.” That, he added, meant that prisoners in Belarus “did not become part of the agenda” before last week’s swap even though Mr. Lukashenko was involved and had agreed to release a jailed German, Rico Krieger.

While Russian activists abroad have put the fate of jailed compatriots at the center of their lobbying efforts, the Belarus opposition has focused on toppling Mr. Lukashenko.

“Unfortunately, many efforts by democratic forces in recent years have not led to the release of people. For a long time, the priority was regime change, which could lead to the release of all political prisoners,” Ms. Kolesnikova’s sister said.

Russian exiles, too, see regime change as their ultimate goal but, mindful that this will probably take many years, have lobbied Western governments to try to secure the release of individual prisoners. They played an important role in pushing Washington to take up the cases of jailed Russian dissidents like Vladimir Kara-Murza and Ilya Yashin, two of the Russians released last Thursday.

Insisting in its message to diplomats that “the issue of political prisoners remains a priority,” Ms. Tikhanovskaya’s office asked Western governments to provide money to fund the International Humanitarian Fund for Victims of Repression in Belarus, a body set up to support former and current prisoners and their families.

But that set off grumbling in some quarters that Ms. Tikhanovskaya’s team, which already receives lavish financial support from the West, was trying to leverage the prisoner issue to extract more money.

Ukraine has launched a surprise ground assault into Russia with troops and armored vehicles, Russian officials and independent military analysts said on Wednesday, in what could be one of the largest Ukrainian incursions onto Russian soil in more than two years of war.

The assault, which began on Tuesday in the Kursk region of western Russia, has resulted in heavy fighting, according to images from the battlefield verified by independent military analysts and Russian statements.

Videos verified by The New York Times showed armored vehicles being struck several miles inside Russia, and Moscow said it had rushed troops and fighter jets to respond. Gen. Valery V. Gerasimov, the commander of Russian forces fighting in Ukraine, said the advance of Ukrainian troops had been halted on Wednesday evening, while pro-Kremlin military bloggers said Ukrainian forces had captured several settlements near the border.

“Alarming news is coming from the Kursk region for the second day,” Igor Artamonov, the governor of the Russian region of Lipetsk, which borders the Kursk region, said on Wednesday. “The Kyiv regime is attacking our borders.”

By Wednesday evening, Ukrainian troops appeared to have advanced several miles into Russian territory, one analyst said, and Russian officials said the fighting was continuing.

The various reports could not be independently verified, and the Ukrainian authorities have not commented on the assault. Two spokesmen for the Ukrainian Army did not immediately respond to requests for comment.

This is not the first time that Ukraine has staged ground attacks across the border into Russia. But while previous assaults were carried out by armed groups of Russian exiles backed by Kyiv’s army, the attack on Tuesday appeared to have directly involved Ukrainian troops, according to Pasi Paroinen of the Black Bird Group, which analyzes footage from the battlefield.

Mr. Paroinen said that a few hundred Ukrainian troops, supported by armored vehicles, had most likely crossed the border on the first day of the attack, and that more soldiers had arrived on the second day. General Gerasimov said that up to 1,000 Ukrainian troops took part in the cross-border attack, a figure that could not be confirmed.

Military analysts said the attack could be an attempt to divert Russian units from the front lines, thus relieving the pressure on Ukrainian troops struggling to contain Russian advances. But they added that the Russian Army had ample reserves of troops to commit to the fight and that the attack risked further stretching Ukraine’s already outnumbered forces.

“Operationally and strategically, this attack makes absolutely zero sense,” Mr. Paroinen said. “This seems like a gross waste of men and resources badly needed elsewhere.”

Russia’s Defense Ministry said the attack started around 8 a.m. on Tuesday with Ukraine’s 22nd Mechanized Brigade attacking border units in the Kursk region, backed by some 30 tanks and armored fighting vehicles. Mr. Paroinen reported “multiple sightings” of Stryker armored fighting vehicles, which the United States sent to Ukraine last year.

Rybar, a prominent Russian military blogger, said on Wednesday that Ukrainian troops had crossed the border at different points, along at least two lines of attack. He said Ukraine had captured three settlements on the first line, which runs north from the Russian village of Nikolayevo-Darino. On the second line of attack, toward the town of Sudzha, Russian troops were “almost completely surrounded” in the village of Oleshnya, Rybar said.

Mr. Paroinen said that Ukrainian troops appeared to have advanced up to five miles north of Nikolayevo-Darino and that they were pushing toward Sudzha.

Ukrainian shelling in the area of the assault killed five civilians and wounded 24 others, according to the Russian state news agency TASS. Alexei Smirnov, the acting governor of the Kursk region, said thousands of residents had evacuated the area of the fighting, most of them by their own means.

President Vladimir V. Putin of Russia said on Wednesday that he would meet with his country’s security services to coordinate a military response to the attacks and that instructions had been given to assist residents of the Kursk region.

Although Ukrainian officials have not officially commented on the attack, Andriy Kovalenko, a senior official focused on Russian disinformation operations, appeared to acknowledge it, writing on Telegram: “Russian soldiers are lying about the controllability of the situation in the Kursk region. Russia does not control the border.”

On Wednesday, Volodymyr Artyukh, the Ukrainian governor of the Sumy region, which sits across from Russia’s Kursk region, ordered the evacuation of some 6,000 residents amid the fighting.

Ukrainian shelling and bombings have in the past targeted Russia’s border regions of Belgorod, Bryansk and Kursk, but cross-border attacks have been rare. The first such attacks reported took place in May of last year, carried out by anti-Kremlin Russian fighters aligned with Ukraine. A similar ground attack took place this March.

On both occasions, the attacks were seen as an attempt to unnerve the Russian public and undermine Mr. Putin’s efforts to insulate them from the war.

But Rob Lee, a senior fellow at the Foreign Policy Research Institute, wrote on social media that those attacks “had little effect on the fighting” in Ukraine and “did not have serious domestic political ramifications for Putin.”

He and other military experts said that if the aim of this week’s attack was to draw Russian troops away from other parts of the front, it had little chance of succeeding.

“Russia already has greater forces/conventional capabilities in the area, better command and control, and it has conscript units that can be deployed, which are not used in Ukraine,” Mr. Lee said. “It is unlikely this operation will force Russia to pull significant forces from Ukraine.”

Sanjana Varghese contributed reporting from London, and Ivan Nechepurenko from Tbilisi, Georgia.

Who sabotaged France’s high-speed train lines last month?

Clear answers to that question have been elusive so far, more than a week after coordinated arson attacks that disrupted rail travel for hundreds of thousands of travelers before the opening ceremony of the Olympic Games.

There have been no arrests, and no suspects have been publicly identified. For now, the country appears far more invested in its Olympic medal count than in the outcome of the investigation. That is probably a good thing for the authorities, because such cases, though not uncommon, are notoriously difficult to solve.

Officials are not ruling out any possibilities, including foreign interference. But much suspicion has fallen on what French authorities label as “ultraleft,” anticapitalist groups that are less interested in gaining notoriety for their actions than in disrupting the workings of the state.

Railway sabotage is a “traditional method of action” for such groups, Gérald Darmanin, France’s interior minister, said in the aftermath of the attacks.

France’s domestic intelligence agency also has said that arson has been “a preferred modus operandi” for the “ultraleft” movement, “which regularly launches campaigns aimed mainly at energy and telecommunications infrastructures.”

But in France and elsewhere in Europe, “the number of arrests for left-wing and anarchist terrorist and extremist offenses is generally not very high,” Europol, the European Union agency for law enforcement cooperation, said in a report last year.

While experts caution that last week’s sabotage case remains open, they also say it bears some hallmarks of the insurrectionary anarchists, who frequently use low-tech methods like arson and cutting cables to target railway or telecommunication sites.

One potential clue being examined by investigators is an anonymous email which was sent a day after the attack to The New York Times and other media organizations and which celebrated the sabotage. It claimed that the attacks were intended to disrupt the Olympics, which the email called a “celebration of nationalism” and a “testing ground” for mass policing that shows how states “subjugate populations.”

It is unclear if the email came from the actual saboteurs, but the Paris prosecutor’s office, which is handling the investigation, said that was being examined. Several experts on far-left movements and sabotage said that the tone and arguments of the email were consistent with an anarchist ideology, and they noted that sabotage carried out by anarchist groups was often followed by similarly fuzzy claims of responsibility.

Victor Cachard, a French author who has written extensively about the history of sabotage, said that it was hard to ascertain with any confidence who was behind the attacks. Still, he said, “when you look at the recent history of claims that come after this kind of action, the insurrectionist anarchist movement is often behind it.”

The email, which was signed “an unexpected delegation,” in a reference to the Olympics, was sent from an anonymous email address created on Riseup, a platform that “provides online communication tools for people and groups working on liberatory social change,” according to its website.

The text of the email criticized France’s weapons export industry, condemned police brutality, castigated French companies like Total or Alstom for wreaking social and environmental havoc and took a dim view of France’s high-speed train system.

“Railroads are not an innocuous infrastructure,” the email said. “They have always been a means of colonizing new territories, a prerequisite for their devastation, and a ready-made path for the extension of capitalism and state control.”

Practically speaking, targeting railway systems or telecommunication networks “requires the least energy for the greatest efficiency,” Mr. Cachard said. France’s rail system is especially vulnerable — too vast to be completely secure, and centralized, with all four main high-speed lines running out of Paris.

That makes creating a bottleneck easy, though train traffic quickly returned to normal after France’s railway company scrambled to repair the damage after the rail attacks. Another spate of vandalism last week against fiber optic cables caused limited disruption.

“The goal of the sabotage is to frustrate the state and to send the message to other groups with similar ideas,” said Thomas Dekeyser, a researcher at Aberystwyth University in Wales who has studied past cases of sabotage in Europe.

He and other experts say that in recent years more activists have become attracted to sabotage. They include climate activists who believe that traditional methods like petitions or protests have made little headway, as well as militants who object to the spread of infrastructure like 5G antennas.

France’s telecommunications infrastructure — phone lines, fiber optic cables, relay antennas — is targeted by about a dozen small-scale acts of vandalism or sabotage every month.

“There is a willingness to push the boundaries, to act not against human life but infrastructure,” Mr. Cachard said. “Throughout history, you see that sabotage goes up a notch when the state is unresponsive to traditional modes of action.”

Indeed, infrastructure sabotage is hardly a new phenomenon.

Aurélien Dubuisson, a historian and affiliated researcher at Sciences Po in Paris, who is an expert on extreme-left movements, said that sabotage was sometimes used in the labor movement’s early days. For instance, figures like Émile Pouget, an anarchist journalist and trade unionist who was active in the late 19th century and early 20th century, advocated such tactics.

Sabotage of railway lines was famously used by French resistance fighters of all political stripes during World War II. Disruptions like temporary power cuts have also been used by French labor unionists opposed to President Emmanuel Macron.

Last year, France’s interior minister said that the authorities were monitoring about 3,000 “ultraleft” activists. But Mr. Dubuisson and other experts caution that officials often use a broad brush that is not always helpful in understanding whom they are talking about.

“It’s a bit of a catchall term,” he said. “The ultraleft label has become a political and media expression for almost anything on the left that involves the use of illegal practices, whether violent or nonviolent, within a political framework.”

And arrests are rare in sabotage cases, making it even more complicated to establish a pattern or blame a specific group, experts say.

Mr. Dekeyser, who made a documentary about a series of arsons and bombs set in the 1980s by an anti-computer group, said that despite a claim published in newspapers under the acronym C.L.O.D.O., the saboteurs were never caught. After two years, the group disappeared.

Insurrectionist anarchists and similar groups are rarely interested in converting the general public to their cause or in using the press or the legal system to their advantage, experts said. They are generally loosely organized, with no formal hierarchy or structure; smaller groups may form to take specific action before disbanding just as quickly.

Anarchists and other fringe, left-wing activists are also accustomed to working with like-minded groups in countries like Italy, Germany or Spain, making it easy to slip across the border, experts say.

In Germany, Tesla was forced to halt production at an assembly plant in March after someone started a fire at a high-voltage pylon that cut electricity to the factory and the surrounding region. A group declaring ties to the antifascist movement claimed responsibility for the attack, but there have been no arrests in this case either.

“They don’t want to draw attention to themselves, but instead focus on action and vulnerability of the infrastructures,” Mr. Dekeyser said of groups like insurrectionist anarchists. “They are not interested in building a platform from which to speak.”

Melissa Eddy contributed reporting from Germany.