Hanging from a ladder attached to the hull of a giant, bobbing tanker, Capt. Efraín Hallax began his climb up to the crew awaiting him atop the Athina, a ship anchored in Panama Bay and third in line to transit the Panama Canal.

The daunting ascent up the shifting ship was nothing new for Captain Hallax, 73. He has been a ship’s pilot in the Panama Canal for over 40 years, responsible for guiding vessels through the trade-critical corridor that connects the Pacific Ocean with the Caribbean Sea.

On this night in February, Captain Hallax reported for work a half-hour before midnight — and just a few hours after President Trump had canceled a call with President José Raúl Mulino of Panama to continue their negotiations over the future of the canal, which the U.S. president wants returned to American control.

The overnight crossing was nothing out of the ordinary for the captain. With about 3 percent of the world’s maritime trade carried through its locks, the Panama Canal is a 24-hour operation.

“Business as usual,” said Captain Hallax. “Always business as usual in the Panama Canal, no matter Christmas, no matter rain, no matter fog, no matter nothing, no matter Trump.”

Xi Jinping wants you to know that he will not be cowed.

Confronted with the latest threat from President Trump of an additional 50 percent tariff on Chinese goods unless Beijing reverses its retaliatory levies on U.S. imports, China’s top leader has remained defiant. His Ministry of Commerce on Tuesday accused the United States of “blackmail” and declared that Beijing would “fight to the end.”

But behind the bravado is a more complicated set of realities for Mr. Xi that makes it politically and economically untenable to offer concessions to the country’s single largest trading partner and chief rival for global influence. With Mr. Trump also refusing to back down, a devastating trade war between the two largest economies may be inevitable — a showdown with painful consequences that will be felt across the world.

The dilemma for Mr. Xi is that looking weak is not an option, but hitting back risks further escalation. The Chinese leader has cast himself as a national savior who is rejuvenating his country’s greatness. As a result, Beijing has less flexibility to back down from a fight with Washington, as other U.S. trading partners like Vietnam have tried, because it could undercut Mr. Xi’s legitimacy, analysts say.

“Beijing’s response to date has emphasized three things: resolve, resilience, and retaliation,” said Julian Gewirtz, a former senior China policy official at the White House and State Department under President Biden who is now writing a book on U.S.-China relations.

“Xi has built up an image of himself as a defiant strongman helming a powerful country, and China’s official messaging is conveying that they are determined to stand up to U.S. pressure even at high costs,” he said.

President Volodymyr Zelensky of Ukraine said on Tuesday that two Chinese citizens fighting alongside Russian forces had been taken as prisoners of war.

Mr. Zelensky said that the two Chinese citizens had been captured while fighting in the Donetsk region of eastern Ukraine. He added that Kyiv had information that “there are many more such Chinese citizens in the enemy’s units,” without providing evidence. The claims could not be independently verified, and there was no immediate comment from the Chinese or Russian governments.

The announcement came at a fraught moment for Ukraine as the Trump administration has seemingly drawn closer to Russia while trying to act as a mediator in cease-fire talks.

Mr. Zelensky on Tuesday did not suggest that the Chinese fighters had been sent by China’s military, but he pointed to their presence as further evidence that President Vladimir V. Putin of Russia was not truly interested in peace.

“Russia’s involvement of China, along with other countries, whether directly or indirectly, in this war in Europe is a clear signal that Putin intends to do anything but end the war. He is looking for ways to continue fighting,” he wrote on social media.

Mr. Zelensky said that he had instructed his foreign minister to “immediately contact Beijing and clarify how China intends to respond to this.” The foreign minister, Andrii Sybiha, confirmed that he had summoned the Chinese chargé d’affaires to demand an explanation.

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Israel’s highest court began hearing a case on Tuesday over Prime Minister Benjamin Netanyahu’s decision to replace one of his top intelligence chiefs — a courtroom battle that could open the door to a constitutional crisis.

The attempt to fire Ronen Bar, the chief of the Shin Bet, has further polarized an already divided Israel. Supporters of the government view Mr. Bar as disloyal to Mr. Netanyahu, and critics consider his removal a dangerous precedent that undermines the independence of democratic institutions.

The hearing, which was being broadcast live in Israel, opened with unruly scenes, as hecklers forced a Supreme Court panel to pause the proceedings and resume them without a public audience. The hearing was likely to last much of the day, and a ruling was not expected on Tuesday.

Here’s what to know about the court case dominating the headlines in Israel today.

What’s the case?

Last month, Mr. Netanyahu fired Ronen Bar, the head of the Shin Bet security service, saying he no longer trusted him. Critics say Mr. Netanyahu fired Mr. Bar in an attempt to seize greater power by purging a dissenting voice from Israel’s security establishment.

As head of the Shin Bet, Mr. Bar helped spearhead Israel’s war in Gaza and oversee the decades-long occupation of the West Bank. He was also one of a handful of senior officials who led the cease-fire negotiations with Hamas to release dozens of the hostages seized during the Oct. 7, 2023, attack that ignited the war.