Teenagers toyed with guns at a museum exhibit. Young men posed in front of posters of the country’s military leader. Over dinner in restaurants, families watched television monitors showing footage of drone strikes.

The event was billed as a national cultural festival in the West African nation of Burkina Faso. But it often resembled a mobilization campaign in the all-out war against the Islamist terrorists who have gradually occupied the country in recent years.

“The motherland or death,” Alaila Ilboudo, a spoken word artist, shouted onstage to the cheers of crowds at the festival, held in May in Bobo-Dioulasso, the country’s second largest city.

Burkina Faso has long been known for its international film festival and arts scene. But as extremists affiliated with the Islamic State and Al Qaeda have turned a swath of West Africa into the world’s epicenter of terrorism, Burkina Faso has been the hardest hit.

More than 8,000 people were killed last year in a conflict between extremists and the military, according to analysts. That is twice as many as in 2022. In a country of 23 million, nearly three million people have fled their homes, according to humanitarian groups, and 1.4 million children are expected to face hunger this summer, with aid corridors choked off by the extremists.

A recent trip across the country and interviews with civilians and analysts revealed a nation torn apart by escalating violence, perpetrated by both the Islamist fighters and the military in its brutal effort to defeat them.

The country is now led by the world’s youngest state leader, Capt. Ibrahim Traoré, a 36-year-old autocrat who seized power in a coup in 2022. He has enlisted Russian military advisers and drafted about 50,000 civilians to fight with his army, leading to a surge of human rights abuses against local populations. Nevertheless, the United States has provided more than half of the country’s humanitarian aid this year — $150 million.

Captain Traoré has silenced activists, lawyers and journalists through forced conscription, imprisonment and disappearances. “Either you fight or you disappear,” he said in a speech in May to draftees.

The military government has denied accusations of targeting civilians or specific ethnic groups in its campaign against the extremists. It did not respond to several requests for comment.

So far, Captain Traoré is losing the battle against the extremists, who freely roam the countryside and lay siege to dozens of towns and cities. In June, more than 100 soldiers were killed in an attack on a military base in Mansila, in eastern Burkina Faso. The Islamists claimed responsibility.

Only the capital, Ouagadougou, and a handful of other areas remain relatively secure.

‘Enemies from within’

Just to reach the cultural festival, which also showcased athletes, many participants had to put their lives at risk.

Germaine Poubéré, a lean 20-year-old wrestler from Soudougui, a village about 300 miles east, said she had to dodge ambushes by the fighters and talk her way through army checkpoints. Once at the festival, she defeated one adversary after another, only to lose in the final round against the national champion.

Between two contests, Ms. Poubéré recalled how she and her family had fled their village, which was under attack by militants, and how she spent the last year out of school. She has since moved back home, but she sometimes sleeps at school because the extremists still attack roads in her area.

“It requires so much courage,” she said.

At the festival, hundreds of soldiers were deployed to provide protection.

Captain Traoré himself was in town, exhorting people to support their military. He regularly urges citizens to turn in neighbors or others accused of collaborating with extremists.

At night, vigilantes gather outside to patrol the streets.

“There are enemies from within. We are on the front line,” said Rasmané Porgo as he kept watch at a roundabout near the festival.

Mr. Porgo, a father of five, believes Captain Traoré will succeed in stamping out the extremists. “Burkina Faso will be stable” in a few years, he said.

For now, much of the country remains unsafe.

Captain Traoré traveled back from the festival to the capital in an armored, nondescript vehicle squeezed in the middle of a speeding convoy of more than a hundred armored pickups and motorcycles. Heavily armed soldiers stationed along the road scanned the bush and ordered all other traffic off the road before he passed.

‘The terrorist Hydra’

In 2014, a movement led by artists, intellectuals and activists pushed out the president of Burkina Faso, who had clung to power for nearly three decades.

Islamist fighters were raging to the north in Mali, but Burkina Faso had been spared from the violence.

Western countries like France and the United States saw a relative haven of stability, sending weapons, special forces and advisers to Burkina Faso to help contain the extremists.

It was a short-lived era.

Militants crept from Mali into Burkina Faso’s north and began staging attacks in 2015, destabilizing the once-peaceful country.

Since he seized power in 2022, Captain Traoré vowed to eradicate what he calls “the terrorist Hydra,” referring to the extremists who have multiplied across Burkina Faso and neighboring countries.

He initially promised to be only an interim leader for a few months until an election could be held. But in May, religious, military and political leaders named him “Supreme leader of the armed forces” and empowered him to lead the country for five more years.

Captain Traoré has ignored calls by Western and West African partners to respect human rights and to abide by the rule of law in his effort to quell the fighters. He has accused the United States and European countries of threatening Burkina Faso’s sovereignty, and last year ordered French special forces based in the country to leave.

On a trip to St. Petersburg last summer Captain Traoré said that President Vladimir V. Putin felt “like family.”

‘Nowhere is safe’

As Amadou, a schoolteacher in eastern Burkina Faso, reached his classroom one morning earlier this year, he said that he saw pro-government, civilian militia fighters searching for people of his ethnic group, the Fulani. His legs shaking, he escaped on his motorbike, he said.

Many ethnic Fulanis are caught between the Islamist fighters, who often invade their villages and recruit them, and the military and civilian militias, which accuse them of being extremists.

Amadou, like many people approached by The New York Times in Burkina Faso, asked that only his first name be used for fear of his safety. He said that he had fled his village years ago because he and his family had refused to follow orders from Islamist fighters that women fully cover themselves and follow their prayer rules.

But now, pro-government militia fighters routinely round up Fulanis with no explanation, he said. “It feels as if nowhere is safe,” Amadou said. “That at any time I can be detained, or worse, because I’m Fulani.”

Soldiers and civilian militia fighters have committed massacres of civilians accused of cooperating with extremists — killings that have gone unpunished, rights groups say.

Women and children have been killed by soldiers, too, according to Fulani representatives and researchers, who have warned the country is approaching a campaign of ethnic cleansing.

“The targeting of civilians has reached mass killing levels,” said Héni Nsaibia, a senior analyst with the Armed Conflict Location & Event Data Project.

Torn families

As the Islamists move closer to some villages and cities, they are tearing families apart.

Under armed guard, a 44-year-old farmer named Zeinabou fled the besieged city of Djibo in April with six of her children. Djibo had been a refuge for Zeinabou and her family after they ran away from extremists attacking their village in 2018.

But Djibo is no longer safe. Zeinabou said she risked abduction or death just by growing peas or millet in nearby fields. She and her husband eventually decided that she would leave for the capital while he stayed behind in Djibo with his second wife and other children.

Now in a Ouagadougou neighborhood sheltering with more than 1,300 people, Zeinabou said she hopes to find work braiding hair to feed her family. For now, though, they rely on people’s generosity.

She said that she has barely been able to talk to her husband and children back in Djibo. But, she added, “We couldn’t think of another option” but to leave.

In the video, the Chinese graduate student stared straight into the camera as she spoke. She wore a mask, but in a bold move, made clear who she was by holding up her identification card. Then she issued an explosive accusation: A prominent professor at a top Chinese university had been sexually harassing her for two years.

Shortly after the woman posted the video on her Chinese social media pages on Sunday, it drew millions of views and set off an online outcry against the professor she named, Wang Guiyuan, then the vice-dean and Communist Party head of Renmin University’s School of Liberal Arts in Beijing.

The next day, Renmin University fired Mr. Wang, saying that officials had investigated the student’s allegations and found that they were true.

The swift response by the university reflected the growing pressure that Chinese academic institutions have come under to curb sexual harassment on campus. In recent years, several schools have been accused of not doing enough to protect their students from tutors and professors who preyed on them.

At the same time, in denouncing the professor, the university and commentaries in state media that followed studiously avoided describing his conduct as sexual harassment. Instead, they depicted it as a moral failing, using language that feminist activists and scholars say points to a strategy of deflection that turns the attention away from victims.

“If they have to avoid saying ‘sexual harassment,’ it’s very hard to imagine that they take sexual violence seriously,” said Feng Yuan, an academic and the founder of an anti-domestic violence help line in Beijing.

In her video, the graduate student, who identified herself as Wang Di, said that Mr. Wang, her doctoral supervisor, had demanded in 2022 to have sex with her, then abused her physically and verbally after she refused.

“Because I rejected him, he retaliated over the past two years, threatening that I would not graduate,” she said in the hourlong video. She included audio clips of what she described as recordings of his attempts to force himself on her. She also said she had text messages that backed up her claims.

Renmin University responded by saying it had verified the student’s allegations and dismissed the professor, whom it identified only by his last name, Wang. In a statement, the school said the professor had “seriously breached the party discipline, school rules and the professional ethics of teachers.”

Mr. Wang, the professor, did not reply to an email seeking comment. Ms. Wang, the student, also did not respond to a request for comment.

The university also said he had been expelled by the Communist Party, and the local police department said it was investigating the situation. An online commentary about the case in the People’s Daily, a Communist Party mouthpiece, hailed the quick action, saying: “Black sheep cannot remain in the herd and the reputation of top schools cannot be destroyed.”

Feminist activists said that school administrators were often more concerned about protecting the reputation of the school than the rights of the victim. Schools in China have long encouraged students to keep quiet about such allegations. In this case, the activists said, administrators may have had little choice but to take action, given the evidence that the student had collected and the widespread scrutiny on the school.

The Chinese authorities have tried to avoid addressing the harm that had been done to the victim, said Lu Pin, a prominent Chinese feminist activist. “It is not a question of rights, it is not a question of safety, but a problem of violating morality and the politics of the party-state,” she said. This was to avoid being seen as encouraging students to seek legal redress, she said.

The avoidance of the term “sexual harassment” has been a feature in past cases as well. In 2023, Southwest University in Chongqing fired a professor after a doctoral student said he had pressured her into having sex with him. In the university’s announcement, it described the teacher as having had an “improper sexual relationship” with a student, a term that scholars like Ms. Feng say is problematic because it implicates the victim as well.

Even though sexual harassment by university teachers of students is officially described as a breach of professional ethics, the tendency within academia was to downplay the issue, said Lao Dongyan, a law professor from Tsinghua University, in a post on Weibo.

Yet “the environment around me seems to collectively assume it a trivial matter, or even an inevitable love affair for the men,” she wrote in the post, which has been liked nine million times.

That Ms. Wang had to resort to going public with her complaint at the cost of her privacy reflected how weak reporting mechanisms on campus can be, Ms. Lu said.

After the university’s response, Ms. Wang posted a statement online saying she was satisfied by the school’s response and appreciative of its concern for her well-being. Her original video was no longer available, though it was not immediately clear who took it down.

More than 10,500 athletes from some 200 countries will participate in the Olympic Games in Paris, but only 15 of them will be from Russia. They will compete without the accompaniment of the Russian flag or its national anthem.

Back in Russia, the competition will not be shown on television for the first time since 1984. And state TV is paying little attention to the Games, other than to point out flaws in the Games in commentary that smacks of sour grapes.

News segments, for instance, have reported on the cleanup of the Seine, which they concluded would inevitably fill up with sewage again. And media commentators expressed disgust that a drag queen carried the Olympic torch — which is antithetical to Russia’s increasing emphasis on what it calls “traditional values” and its crackdown on L.G.B.T.Q. expression.

It’s quite a comedown for Russia, a traditional Olympic powerhouse that for years used the competition as a way to project power and foster national pride, and often finished first in the final medal count. And it represents the price the country is paying for its invasion of Ukraine two years ago and the daily mayhem it inflicts there.

Banned from participating because of the war, Moscow has chosen to spurn the Games in return. It is framing them as part of the same narrative that President Vladimir V. Putin has used to stoke nationalism at home: that Russia is engaged in an existential standoff with a Western alliance bent on the country’s humiliation.

“No one wants to recognize the real reason for the increased barriers to Russia’s participation,” said Dmitri Navosha, a Belarusian who co-founded a prominent sports website in Russia but has left the country and opposes the invasion of Ukraine. “The reason is the war.” And in Russia, he said, “this fact is simply hidden and interpreted as ‘the West doesn’t like Russia, so they don’t let us go anywhere.’”

Still, the Kremlin and its supporters insist the decision to bar Russia is borne of American hypocrisy.

“So now we mix sports and politics?” Dmitri V. Gubernyev, a well-known Russian sports announcer, said in an interview. “Americans, who went to Iraq and later acknowledged the mistake,” he added, implying that the United States was never sanctioned in the sports world for waging wars. “And who invaded Vietnam, acknowledged later — not by you and me, but by Biden — as a mistake?”

In 2017, the International Olympic Committee suspended Russia’s team from participating until the end of 2022 because of a doping scandal. Even so, it sent some of the largest contingents to the Games — 335 in Tokyo three years ago — where Russian athletes participated and won medals under a “neutral” designation.

In 2022, the I.O.C. banned Russian athletes again in the wake of the full-scale invasion of Ukraine. The suspension also extends to athletes from Belarus, Russia’s neighboring vassal state, whose leader, Aleksandr G. Lukashenko, has supported Mr. Putin’s invasion of Ukraine.

Last year, the I.O.C. decided to allow individual Russian athletes to participate if they met strict requirements for participation.

Russian and Belarusian athletes and personnel “who actively support the war” or are contracted to their country’s military or national security agencies are ineligible to participate.

The I.O.C. also ruled that no Russian or Belarusian state official could be accredited for the Games. Many media representatives from both countries were also prohibited from attending, further irritating the Kremlin.

Russian sports organizations, commentators and general society are divided over participation in these circumstances.

The head of Russia’s Olympic Committee, Stanislav Pozdnyakov, has maligned the athletes who chose to participate, in part because about half of them are based outside of Russia. He called them “foreign agents,” a derogatory designation for people the authorities consider to be working against the national interest.

The Russian Olympic Committee has also made payouts of more than 200 million rubles, or $2.3 million, to at least 245 athletes who could not or chose not to compete, the body’s director general told RIA Novosti.

There was a public pressure campaign inside Russia to persuade athletes to withdraw. At least 20 Russian athletes who qualified and met the criteria for competing rejected the invitations — either because their federation decided not to participate or out of solidarity with other team members who were not greenlit by the Olympic committee.

In a statement, the Russian Wrestling Federation said that it “would not allow the spirit of the Russian team to be broken.” The group said it would rather none of its athletes participate than only a few who qualified.

The judo team also complained that “of the 17 judokas who received the Olympic rating, the I.O.C. allowed only four to participate in the Olympics.” It refused to let those who qualified to compete under what it called “humiliating conditions.”

The Kremlin has left the thorny decisions on who should participate to the federations and their athletes.

“Each athlete makes such decisions independently,” said the Kremlin spokesman Dmitri S. Peskov. “As for those who had the opportunity and did not go, each federation has its own circumstances, agreements, collective opinions and decisions. This needs to be respected.”

Ukraine has actively lobbied against some athletes who are participating. For instance, it called for the I.O.C. to exclude the Russian gymnast Angela Bladtseva, 18, from trampoline jumping. Kommersant, a Russian business daily, reported that Ukrainian officials had complained because Ms. Bladtseva competed in the Russian city of Krasnodar last year against a background with the pro-war symbol “Z” and the slogan “We do not abandon our own.” She will participate in the Paris Games.

The war has caused other divisions over Russia’s Olympic participation. Military bloggers, who are generally full-throated supporters of Russia’s army, have criticized St. Petersburg for offering cash awards to athletes who earn medals, calling it a form of betrayal.

“We are literally collecting pennies to help the front throughout the country, while they are paying traitors,” wrote one blogger with 257,000 followers on Telegram, using a slur for L.G.B.T.Q. people to refer to those who proposed the payments.

The scant Russian presence this year feels like a repetition of the 1980s, said Mr. Navosha, the founder of the sports website. The United States led a boycott of the 1980 Moscow Olympics in protest of the Soviet invasion of Afghanistan, leading to a Russian boycott of the 1984 Los Angeles Games.

“We have a very clear historical parallel that directly indicates where Russia is now — exactly where the Soviet Union was in 1980,” he said. “A direct, undisguised confrontation with the Western world, in which sport became an instrument of the confrontation.”

There is one notable difference, he added. In 1984, the Soviet Union organized its own Olympic-style competition, Druzhba-84, or the Friendship Games. The event was portrayed as evidence that the socialist way of life “provides more favorable facilities for the human beings’ all-round physical and spiritual development.” Athletes from about 50 countries participated.

This time around, a version known as Druzhba-24, was scheduled to take place in September by Mr. Putin’s decree. Organizers allocated money and planned competition in more than 30 summer sports, but it was postponed until at least next year, Mr. Navosha said, a sign that not enough countries were on board to compete.

“We understand that Russia’s circle of allies is much smaller now than it was back then, and it is too small to hold their ersatz Olympics,” said Mr. Navosha.

Mr. Gubernyev, the announcer, said he was in favor of all athletes who qualified competing, even if he believed the conditions were unfair. He added that he, like other Russians who love sports, would find a way to watch the games.

But he warned that the exclusion from Paris would foster resentment in a generation of athletes, and Russians in general against the West: “A person does sports to win an Olympic medal.”

“Against the background of these decisions, another round of confrontation will be born,” he added. “Because there are people who really want to broaden their horizons, see Europe and show the world what they can do. That wasn’t given to them, so their response will wind up being, ‘Go to hell.’”

Alina Lobzina and Ivan Nechepurenko contributed reporting.

The Ukrainian authorities detained a suspect on Thursday in the killing of Iryna Farion, a divisive far-right Ukrainian politician who was shot dead by a gunman last week in the western city of Lviv, a crime that shocked the nation.

Ihor Klymenko, Ukraine’s interior minister, said in a statement that there was “sufficient evidence” that the suspect, whom he identified only as an 18-year-old man, had killed Ms. Farion. He said the suspect had been arrested in his hometown, Dnipro, a large city more than 500 miles east of Lviv in eastern Ukraine.

Mr. Klymenko added that a preliminary investigation suggested that the suspect had worked with others to plan the killing. He added that the suspect, while preparing for the killing for at least two months, had “rented at least three apartments in Lviv.” Mr. Klymenko did not rule out the possibility of Russian involvement.

Ms. Farion died on Friday after an unknown assailant shot her in broad daylight near her home in Lviv. Witnesses told Ukrainian news outlets that the killer fired a single shot and quickly fled.

For nearly a week, the Ukrainian police had been searching for a suspect who had appeared on surveillance cameras and was described as a man in his 20s. Mr. Klymenko and President Volodymyr Zelensky said hundreds of security agents and investigators had been deployed to find him.

“They checked every corner along the gunman’s escape route” and searched about 250 acres of forest, Mr. Klymenko said of the police. “Eventually, the suspect was tracked down.”

The killing last Friday of Ms. Farion, a former lawmaker and award-winning linguist, sent chills through the country, where there had been no high-profile killings since Russia began its full-scale invasion of Ukraine in 2022. Given Mr. Farion’s controversial profile, some Ukrainians feared that her death would polarize Ukrainian society.

Ms. Farion was a highly divisive figure in Ukraine. She belonged to Svoboda, a hard-line nationalist party, and some Ukrainians despised her for her denunciation of Russian-speaking fighters in the Ukrainian army. Ukraine is a bilingual country, and many Ukrainians speak Russian, especially in eastern regions closer to Russia.

In November, the Ukrainian security services opened a criminal investigation into Ms. Farion’s statements. She was also fired from Lviv Polytechnic National University, where she taught.

Ms. Farion remained a respected linguist, and several thousand mourners attended her funeral on Monday in Lviv. Supporters described her as a true patriot and a pioneer of current efforts to promote the use of Ukrainian, once banned by the Soviet authorities.

Political analysts and officials said it was crucial to conduct a swift and transparent investigation to keep rumors from spreading.

Yaroslav Yurchyshyn, the head of the Ukrainian Parliament’s committee on freedom of speech and a liberal politician, wrote on Facebook last week that the killing could increase distrust of the Ukrainian police and pit rival political parties against each other. Like other Ukrainian officials, he suggested that Moscow might have been behind the killing in an attempt to sow divisions.

On Thursday, the Ukrainian police said they were examining unverified claims linking the killing to a Russian neo-Nazi group.

Helicopters whirling overhead. Police demanding a QR code and proof of identity to pass. Metal fences barricading the streets. And an army brigade, marching by in formation, machine guns hoisted to their chests.

This is what it has been like getting to the front door of my apartment building for the past few evenings.

It’s a weird moment in Paris, on the eve of the Olympic Games and its unusual opening ceremony. The heart of the city has been transformed into a fortress, with metal barricades and checkpoints, subway stations shuttered, 45,000 police officers — about 10 times more than normal — on top of 10,000 soldiers, search dogs, bomb squads and tactical teams, including in helicopters.

The Seine’s banks and bridges, normally teeming with humanity, are suddenly empty. A strange, exquisite calm has descended.

The reason: After all its hand-wringing over a Plan B, Paris is proceeding with its risky and wonderful plan to float the opening ceremony — with the world’s best athletes — down the Seine, through the center of the ancient city and before more than 400,000 spectators packed into stands and leaning out of windows.

Even if Paris weren’t scarred by terrorist attacks, protecting all those people forms an obvious — and heavy — security challenge.

Officials warned us for months of their plans: On July 18, eight days before the opening ceremony, they set up a security zone on both sides of the river, putting up some 44,000 metal fences and manning each corner with police. Anyone who wanted to get inside the so-called gray zone needed to apply to the police for a QR code and then produce it on request — whether it was to go home, get to work or make a restaurant date. Some 200,000 people applied and were screened.

At the same time, the police entered some 500 buildings inside the secured area, examining stairwells and basement caves, interior ministry officials said. They’ve searched the sewers, sealed thousands of manhole covers and scoured through the city’s underground network of catacombs.

And police imposed what amounts to house arrest on 155 people who were considered to be potential threats.

As the start of the ceremony on Friday evening approaches, the security will get even more intense. The restricted zone will expand. More subway stations will close. Police officers will up take positions on rooftops, and the airspace over and around Paris for 93 miles will be closed, with all four nearby airports shuttered, including Charles de Gaulle, Europe’s third-largest.

This unusually heavy blanket has irritated some locals, particularly business owners, and bewildered many tourists trying to understand the directions proffered in broken English by police officers.

“We just wanted to go to Notre-Dame and now … what is this?” said Darius Emadi, 38, an American professional clown who just moved to Paris and was clueless about the closures and codes as he stewed, stuck behind a checkpoint near City Hall.

“I’m never going to make it to my doctor’s appointment!” complained a woman stopped near the silver Bir-Hakeim Bridge.

The heightened security has also infringed on human rights, according to some lawyers contesting the house arrest orders.

“These administrative orders destroy lives; they amount to social deaths for people who are not even identified as a threat by the police,” said one lawyer, Samy Djemaoun. “It’s not a case-by-case approach. It’s an across-the-board one.”

Terrorism was the reason the Paris mayor agreed to lobby for the Olympics in the first place, and why organizers pushed for such an atypical, exposed opening ceremony. It would be a sign of hope and freedom for a wounded city, after two attacks by Islamist extremists killed nearly 150 and wounded more than 400 people in 2015. Since then, the country has endured dozens more attacks — the latest in December, when a man with a knife and hammer killed a tourist and injured three others near the Eiffel Tower.

“I totally agree with all the security measures they put in place because you never know,” said Clarissa Jimenez, 25, stepping out of the hair salon in the Passy neighborhood where she works.

“In the beginning, I found it all kind of scary,” she said, “but now I feel safe.”

The police and French security services dragnet has yielded some results. In central France, a man of Chechen origin was charged in the planning of an attack outside an Olympic soccer match. Another man, a neo-Nazi sympathizer living in the Alsace region, was sentenced to two years in prison for publishing an explosives recipe online and for making threats. This week, a 40-year-old Russian man was charged with working at the behest of a foreign power to “provoke hostilities” in France intending to destabilize the Olympic Games.

Police checks have vetted about a million people involved in the Games, including security guards, stadium workers and volunteers. Of those, about 5,000 were rejected because of their criminal records, the authorities said, or because they had been flagged for “radicalization.”

But 5,000 out of one million was a low number, the interior minister, Gérald Darmanin, said during his media tour of reassurance this week.

“We are very confident, but obviously very, very focused,” Mr. Darmanin said. “We have perceived no clear threat targeting the Olympic Games — neither the French intelligence services, nor the services of foreign services helping us.”

Security experts say that given the police density and preparation, the risk of a major terrorist attack on the ceremony is very low. A greater concern is an isolated person with a knife outside the security zone, said Guillaume Farde, a security expert who teaches at Sciences Po in Paris.

“Even if the reaction time with that density of police in Paris is in the order of dozens of seconds, in dozens of seconds you can make a victim,” he said. “That’s very, very hard to control or anticipate.”

To guard against that possibility, police have poured into the city from across the country. They received handwritten instructions from Mr. Darmanin this week to be thorough and professional, but also friendly: “the most beautiful face of France.” He echoed General Dwight D. Eisenhower’s famous message to American soldiers on the eve of the D-Day landings, 80 years ago: “The eyes of the world will be fixed on you. Your job will not be easy.”

Many Parisians have noticed the change in tone.

“The police officers are charming,” Florence Bellamy said as she walked through the desolate protected zone one morning with her QR code. Last Monday was her 71st birthday and she said she felt as if the Olympics had emptied out the city center, and was offering it up to her as a present.

She wandered across the Seine and visited old haunts, stopping at Café de Flore, where Jean-Paul Sartre and Simone de Beauvoir once hung out, for a café crème.

“I had the feeling that all of Paris belonged to me,” said Ms. Bellamy, a writer and French teacher, “and I would never see it like this again.”

The day after the ceremony, if everything goes smoothly, most of the fences and checkpoints are scheduled to come down. No more QR codes. One third of the police officers will leave. The ones who remain will spread out across the city and suburbs. And the Olympic Games will begin in earnest.

“All this will be quickly forgotten,” Mayor Anne Hidalgo said during a welcome cocktail at City Hall this week. “After the ceremony, when they pull down all the fences and people can see all the beautiful spaces, there will be joy.”

Ségolène Le Stradic contributed reporting.

The Baltic Sea floor is full of secrets.

Untold thousands of sailors have died beneath its cold waves, some lost to battle, some to weather and rocks. With them sank their ships — and their treasure.

This month, a Polish diving team slipped below the sea’s surface to check out a small wreck, just a few miles off Sweden. A first pass revealed a small, seemingly unremarkable merchant ship about 58 meters (190 feet) beneath the surface. But Tomasz Stachura, who leads the Baltictech diving group, had a hunch.

The next morning, he returned. This time, he found crates and crates of what appeared to be Champagne, along with wine and porcelain, almost as if the ship’s cargo had been headed to a party.

“We realized that this was a kind of treasure,” he said. He took photos and cleaned the labels, but they were illegible. However, the shape of the bottles suggested that they contained Champagne, he said. Looking closer, he saw bubbles. “It came to me that, perhaps, they are drinkable.”

The wreck itself is hardly novel: Some 100,000 sunken ships dot the Baltic seabed, said Jim Hansson, a maritime archaeologist at the Vrak Museum of Wrecks in Sweden.

But finding Champagne would be a marvel. “It’s not so common,” he said, between dives with the Swedish Coast Guard.

Sparkling wine may have been even more of a luxury than it is today in the mid-1800s, which is when Mr. Stachura thinks the ship may have sunk. (An archaeologist analyzed bottles of mineral water, a relic of an earlier health food craze, from the wreck, and said the labels were from 1850 to 1876.)

It is not the first time that alcohol has been found aboard a shipwreck in the Baltic Sea.

In 2019, cases of cognac were found on a Swedish steamship that had sank in 1917 after being attacked by a German submarine in World War I. And in 2010, divers found bottles of Champagne, some of which appeared to have been bottled before 1830.

“I wouldn’t call them pleasurable drinks,” said Essi Avellan, a Champagne expert in Finland who tasted some of the bottles from that wreck found in 2010. “But, of course, it’s like drinking history.”

The drinkability all depends on how well it was sealed, said David T. Smith, a British drinks writer and consultant who once tasted a shipwrecked gin — with unexpected seawater notes. (“Disgusting.”)

“I don’t know, necessarily, how good it would taste,” he cautioned, of the recent discovery of sparkling wine.

On the other hand, the sea could act like a preservative, Ms. Avellan said: No oxygen can come through the cork. “It would probably taste more youthful than a wine that had been aging at the winery,” she said.

The water itself is also cool and dark, just like a wine cellar. (It’s pressurized, too, which is good for sparkling wines like Champagne.) And the salinity is lower in a sea than in an ocean, so wrecks are better preserved.

“It’s a frozen time capsule,” said Johan Rönnby, a professor of maritime archaeology at Södertörn University in Sweden, who may research the wreck with Mr. Stachura.

For now, the wreck — and the divers — are in a holding pattern. Mr. Stachura reported the find to Swedish authorities. Now, he is waiting for permission to work with maritime archaeologists like Dr. Ronnby to conduct underwater research and, possibly, targeted excavations of the cargo. Approvals may take some time.

For now, the ongoing research is happening on land. Mr. Stachura thinks he just might have identified the ship as one that Czar Nicholas I of Russia lost in 1852. Right time, right route, right client profile.

Eventually, perhaps, he may taste the sparkling wine himself.

“If some expert says it’s drinkable?” he said. “Yes, yes, why not? It would be nice to try what people would drink 170 years ago.”