Up to the last minute, Isaac Presburger, like a lot of other Mexican businessmen, still could not believe that President Trump would deliver on his promise to hit Mexico with tariffs. Little did it matter that Mr. Trump had announced that very day that he would go ahead with the planned taxes.

“I am still incredulous,” said Mr. Presburger, director of sales at Preslow, a family-run apparel business in Mexico. “We know by now that Trump pressures you so you give him what he wants. We have given him everything and he has not let loose of his grip.”

In response to Mr. Trump’s threat to impose 25 percent tariffs on Mexican products, Mexico made a major effort: Leaders agreed to send more than two dozen alleged cartel heads to be tried in the United States, a departure from the government’s previous stance on extraditions.

President Claudia Sheinbaum dispatched thousands of National Guard troops to the state of Sinaloa, the hub of fentanyl trafficking, where they seized vast amounts of the synthetic opioid and busted hundreds of laboratories. She sent thousands more to the U.S. border, contributing to a plunge in the number of illegal crossings.

Ms. Sheinbaum bent further than anyone had expected to show the Trump administration that her government was serious about meeting U.S. demands, analysts say.

And yet, in spite of it all, the tariffs struck after midnight on Tuesday.

That has left people in Mexico’s government, business and civil society reeling, but also feeling exasperated, even betrayed.

“We are emphatic,” Ms. Sheinbaum said in a news conference on Tuesday morning, hours after Mr. Trump’s tariffs took effect on its biggest trading partners, including Mexico and Canada. “There is no reason, justification or excuse that supports this decision that will affect our people and nations.”

She ticked off what she described as her government’s “significant actions” against organized crime, and noted a 50 percent drop in fentanyl seizures between October and January at the U.S.-Mexico border.

“We have worked and delivered results on security matters,” she said.

The tariffs represent not just a rift in the fabric of two economies that have been deeply interwoven for decades, but a sudden departure from a relationship that had long been collaborative and from what many in Mexico expected would take place: a last-minute deal.

Through late last week, a delegation from Mexico had been frantically negotiating with officials in Washington, and leaders had been projecting confidence. Even the financial markets held steady in Mexico.

Mexico’s economy minister, Marcelo Ebrard, posted to social media on Friday, “Mexico and the United States have a great future working together,” with three thumbs-up emojis. Business leaders across the country shared the same optimism until Monday.

José de Jesús Rodríguez, president of Mexico City’s chamber of commerce, said Mr. Trump’s decision surprised him, particularly in light of the American leader’s suggestion that he would not impose tariffs if Mexico produced results on migration and drug trafficking. The results it delivered included a barrage of high-level arrests and the handover of the 29 accused drug bosses that the U.S. government had long sought to get on its own soil.

But Mr. Trump, whose criticism of Mexico had focused on illegal fentanyl, shifted his terms on Monday, saying that Canada and Mexico needed to relocate automotive factories and other manufacturing to the United States. “What they have to do is build their car plants, frankly, and other things in the United States, in which case they have no tariffs,” he said.

“It is extremely disappointing and frustrating,” Mr. Rodríguez said. “The United States broke their word, and it dictates the future of our commercial relationship.”

“It’s time for us to look to other regions,” he added.

Ms. Sheinbaum said she had a call scheduled with Mr. Trump for Thursday, and told reporters on Tuesday that if the tariffs remained in effect afterward, her government would go ahead with a number countermeasures, including retaliatory taxes, which would be announced on Sunday. Canada also announced reciprocal tariffs.

“We don’t want to enter into a trade war,” she said. “That only affects the people.”

Ms. Sheinbaum’s approval ratings in Mexico have soared, with many praising her coolheaded approach to handling Mr. Trump, who called her a “wonderful woman.”

But the trade wars that are now underway will test not only that relationship but how much the government can insulate its economy and its population from chaos and pain.

Mr. Presburger, the Preslow sales director, said that he still hoped the tariffs wouldn’t last more than a few days, or that Mr. Trump would change his mind. Otherwise, “it will be disastrous for Mexico.”

The United States buys more than three quarters of Mexico’s exports, and tariffs will hit manufacturing, agriculture and other businesses, immediately disrupting the supply chain and most likely raising the cost of Mexican goods sold in the United States.

Just hours before the tariffs went into effect, Manuel Sotelo, president of the association of transporters of Ciudad Juárez, said the uncertainty hovered over the many who truck goods into the United States.

He said if tariffs applied to all Mexican products, they would affect everyone. But if they also applied to raw materials coming from businesses on the border, “then the situation is going to get worse for the region.”

He said the transportation industry could not last even a week if trade were frozen.

When Mr. Trump hit Mexico with tariffs during his first term, it carried out a surgical response, targeting the retaliatory tariffs at products that were produced in Republican states considered part of Trump’s base — such as Kentucky bourbon.

The tariffs were lifted after about a year.

Preparing for the worst, Mexican business owners and trade groups were already starting to scramble.

Antonio Lancaster, president of the council of industrial chambers of the state of Jalisco, one of the largest exporters of food and beverages — including tequila — to the United States, said the chambers’ leaders were already in talks with the state and federal government about plans to bolster local production and pursue other export markets.

“We saw this coming, and this means we will pursue a rearrangement of our exports,” Mr. Lancaster said. He added, “We will end up exporting to Europe, Asia or anywhere else.”

Businessmen like Mr. Lancaster argued that the tariffs will ultimately end up hurting American consumers as well as Mexican producers.

“We all lose here,” he said.

Jesús Manuel Salayandía, coordinator of a business group on the border, said that corporate leaders mostly based in the United States have been meeting to plan their response to the tariffs.

“They are analyzing whether they will move to Central America, to the southern part of the country, if they will return to the United States, or if they will automate or robotize certain production lines,” he said. “All of that is being considered.”

Mr. Salayandía said that the Mexican government, perhaps expecting a last-minute deal, had not worked to prepare.

They had been thinking, “Let’s wait for Trump to tell us what will happen,” he said. “But they’re not working on a plan to strengthen the domestic market or to offer incentives to the companies already here.”

Marcelo Vázquez, state delegate of the National Association of Importers and Exporters of the Mexican Republic in Chihuahua, said for the last few weeks some companies had workers on duty virtually around the clock to export goods into the United States before the tariffs came into effect.

“But that’s just an aspirin for the headache; it doesn’t really solve the problem.”

Rocío Gallegos contributed reporting from Ciudad Juárez, Mexico.

The alarms about Joël Le Scouarnec’s sexual desire for children had been ringing for years, well before he was charged with raping or sexually assaulting 299 people, most of them children under his care when he was a surgeon.

His wife’s sister said she expressed concerns to her sister after she thought she had witnessed him kissing her daughter’s bottom, according to court documents. His own sister confronted him directly after her youngest daughter told her “in children’s words” that he had touched her. And he had already been convicted in 2005 of possessing child sexual abuse imagery, and given a suspended sentence.

“Nothing, nothing, nothing,” Marie-France Lhermitte, now his former wife, said as the mass child sex abuse trial opened last week. She was responding to a question posed repeatedly about whether there were warning signs that she should have acted upon.

Mr. Le Scouarnec was a gastric surgeon who worked for more than three decades in multiple clinics and private hospitals in western and central France before he was arrested in 2017 for exposing himself to a 6-year-old neighbor. That arrest, and the police search of his home, led to the discovery of evidence — diaries and other writings — of much wider abuse over 25 years. In 2020, he was convicted of sexually assaulting or raping four little girls, including his sister’s two young daughters, and is serving time.

The latest trial — considered the country’s largest ever pedophilia case — is based mainly on those diaries and writings, which investigators used to identify the hundreds of listed victims.

Mr. Le Scouarnec, now 74, has admitted to the “vast majority” of the charges against him, his lawyer Maxime Tessier told the court in Vannes, where the trial is being held. The rape charges are mostly related to touching or penetrating children’s vaginas and anuses with his fingers. He has denied some of those charges on the grounds that those were part of medical procedures.

Throughout the first days of the trial, Mr. Le Scouarnec, who lost his medical license in 2017, has repeatedly voiced remorse for ruining not just his family’s lives, but also those of his former patients. Many of them are now adults and watch the proceedings from a nearby auditorium as support dogs wander the aisles. Many are expected to testify.

In the trial’s first week, the judges, the main prosecutor and lawyers for the former patients tried to uncover the roots of Mr. Le Scouarnec’s desire to sexually touch children. They also were trying to understand how he got away with abuses for a quarter-century without anyone in his family moving to stop him, despite at least some of them having suspicions.

In testimony, his three sons, two siblings, former wife, a cousin and a close family friend painted a portrait of a tight-knit family riven with sexual abuse and infused with a culture of silence and secrecy.

Mr. Le Scouarnec’s son Fabien Le Scouarnec testified that his grandfather Joseph Le Scouarnec had sexually abused him. (The grandfather, now deceased, had told people during his lifetime that he was himself abused, the court heard.) Mr. Le Scouarnec’s sister, Annie Jobard, said that she was raped by two boys when she was 14 and had never told her family.

His former wife said she had been raped by two male relatives when she was a child. She kept it a secret, she said, even from her husband.

“When you are raped, you feel dirty,” she testified. “So, you don’t talk about it.”

Family members described Mr. Le Scouarnec as a good husband, good brother and good father who loved reading and opera and who worked long hours.

His three sons said he was not home often, but when he was, he helped them with studies, took them to museums and ensured that they had music lessons. They described their childhoods as happy. Their father never abused them and they were completely unaware of his pedophilia, they said.

“We had everything we needed to be happy, and perversion exploded like an atomic bomb throughout the family,” Fabien, 42, said.

“It’s Dr. Jekyll and Mr. Hyde,” he later added. “There is a part of my father’s personality that I don’t know.”

But Mr. Le Scouarnec’s sister, Ms. Jobard, knew of at least one case. She told the court that she had confronted her brother in 2000, after her younger daughter told her the reason she did not want to go to dinner with him: He had been sexually abusing her. Chain-smoking in her car, Mr. Le Scouarnec admitted to the abuse and said he would work the rest of his life to make amends, she testified in court. She said she told him to get treatment.

Asked why she did not go to the police back then, Ms. Jobard said she thought her youngest daughter was the only victim. At the time, she did not know that Mr. Le Scouarnec had also victimized her elder daughter.

“I didn’t realize he was someone dangerous,” said Ms. Jobard, now 72, a retired English teacher. “For me, it was inconceivable that my brother was someone like that.”

Even when she later learned that Mr. Le Scouarnec had been arrested on charges of owning child sexual abuse imagery, and after Fabien told her about the abuse he had suffered from his grandfather, she said she did not make the connection that there was a much deeper problem in the family.

In retrospect, she said, “I think it was denial.”

Ms. Lhermitte, Mr. Le Scouarnec’s former wife, also testified.

Sitting in a swivel chair in the middle of the courtroom, she denied that her sister, whom she called a birdbrain, or her sister-in-law, Ms. Jobard, had ever spoken to her about their fears he was abusing their children.

She also said she did not know that her husband had been convicted of owning child sexual abuse images, despite having been at home when the police arrived to search the house. She went shopping during the search, she said, and when she returned, her husband was relaxed and told her it was all a big mistake.

She separated from him soon after the police search, but divorced him only more recently and continues to visit him in prison.

When Aude Buresi, the presiding judge, asked her about her sessions with a psychiatrist and whether they had helped her to understand the root of abuse in her family, she refused to talk about it, stating that it was her private life.

Judge Buresi tried to force her to confront the abuse by projecting photographs found on her husband’s many confiscated hard drives onto screens in the courtroom. They revealed naked, intimate pictures of the two nieces he was convicted of abusing.

“You are destroying us,” she said to the judge, adding later: “It’s so abusive of you. I don’t have the intellect to take in all that. I don’t know how I will survive that.”

Testifying in court this week, Mr. Le Scouarnec repeatedly defended Ms. Lhermitte, whom he still referred to as his wife. He argued that he had lied to her for 30 years, though he said she knew “some things” without giving details.

“I had two lives,” said Mr. Le Scouarnec, who was mostly composed as he addressed the court. “A family life, a social life, a professional life, and next to that, the life of a pedo-criminal, a pedophile who thought of nothing else.”

But he was also vague when asked key questions, like why he had destroyed some of his diaries. Most often he answered that he did not remember.

Though the court spent days demanding illumination from Mr. Le Scouarnec’s relatives and then from him, the source of his pedophilia remained elusive.

Ms. Jobard tearfully asked him if their father had also abused him.

Mr. Le Scouarnec stood up in the courtroom’s glassed-in box for the accused to offer a response.

“I have talked to psychologists for a very long time, I asked this myself, and I still don’t know,” he said. “What I am certain of, and I repeat: I was never abused by anyone.”

The next day, addressing his elder son Renan Le Scouarnec for what he said might be the last time, he caused a commotion in the courtroom when he disclosed another distressing family secret.

“I acknowledge having committed acts of sexual abuse on my granddaughter,” he said.

Then he asked for his son’s forgiveness.

The court abruptly adjourned as the son and son’s wife were whisked away into the care of two psychologists.

The C.I.A. director John Ratcliffe said on Wednesday that intelligence sharing with Ukraine had been paused alongside military aid to pressure its government to cooperate with the Trump administration’s plans to end the country’s war with Russia.

Speaking on Fox Business, Mr. Ratcliffe applauded the Ukrainian president Volodymyr Zelensky’s statement on Tuesday praising President Trump and insisting that he supported peace with Russia. Mr. Ratcliffe said he thought intelligence sharing would resume.

“President Zelensky put out a statement that said, ‘I am ready for peace and I want President Donald Trump’s leadership to bring about that peace,’” Mr. Ratcliffe said. “And so I think on the military front and the intelligence front, the pause that allowed that to happen, I think will go away, and I think we’ll work shoulder to shoulder with Ukraine as we have, to push back on the aggression that’s there.”

On Tuesday, after Mr. Trump ordered a halt to military assistance, officials differed on whether the United States was continuing to share intelligence. One official said all intelligence that was not directly related to the protection of Ukrainian troops had been put on hold. Another official said that exception covered most intelligence sharing, and information still was flowing to Ukrainian forces.

Mr. Ratcliffe said on Wednesday that Mr. Trump asked for a pause on intelligence sharing. And his comments suggest that the C.I.A. put at least some of its intelligence sharing with Ukraine on hold for a short time.

Trump administration officials have said the pauses were a warning to the Ukrainians of the consequences if they did not cooperate with Mr. Trump’s peace plan. The details of those plans remain unclear. Mr. Trump has spoken approvingly of President Vladimir V. Putin of Russia, and his aides have endorsed elements of the country’s ideas for ending the war.

But European countries are trying to develop their own plan that could win over both Mr. Trump and Mr. Zelensky.

King Charles III flew by helicopter to the H.M.S. Prince of Wales in the English Channel on Tuesday, where he mingled with sailors and watched as fighter jets took off from the deck of the ship, a Royal Navy aircraft carrier. It might have been a welcome getaway from his suddenly complicated social life.

In the span of five days, Charles had invited President Trump for a rare second state visit to Britain and then played host to two of Mr. Trump’s biggest antagonists, President Volodymyr Zelensky of Ukraine and Prime Minister Justin Trudeau of Canada, at his country estate northeast of London.

None of those gestures by Charles was overtly political. As is customary in Britain’s constitutional monarchy, he acted at the behest of the government. But they have nevertheless drawn the 76-year-old king into a swirling diplomatic drama in a way that is almost unheard-of for a British sovereign.

Charles’s invitation to Mr. Trump, delivered with much fanfare by Prime Minister Keir Starmer on Thursday in the Oval Office, has become more contentious since the president clashed with Mr. Zelensky over American support for Ukraine the day after his more harmonious session with Mr. Starmer.

“Now Stop the State Visit for ‘Bully’ Trump,” The Mail on Sunday, a right-wing tabloid, said on its front page. It cited a chorus of demands by lawmakers and other critics that the government rescind the invitation to Mr. Trump to telegraph Britain’s displeasure with the president and solidarity with Ukraine.

Symbolically, Charles may have done the next best thing: hosting Mr. Zelensky at his estate, Sandringham, after the president attended a summit meeting on Sunday devoted to Ukraine. Buckingham Palace did not disclose what they talked about but said Mr. Zelensky was “warmly received” by Charles, who served him tea in Sandringham’s Saloon room.

For Mr. Trump’s critics, the icing on the cake came on Monday, when Mr. Trudeau, whose country has come under sweeping American tariffs and which Mr. Trump says he wants to annex as the 51st state, made the pilgrimage to Sandringham to meet Charles. The king, of course, is also Canada’s ceremonial head of state.

Mr. Trudeau said in a social media post that they discussed “matters of importance to Canadians — including, above all, Canada’s sovereign and independent future.” Charles himself was silent, which frustrated some Canadian politicians, who argued that he should have publicly reaffirmed Canada’s sovereignty. Given his nonpolitical role, that was not going to happen. But the symbolism of the sovereign, smiling as he greeted a prime minister whom Mr. Trump refers to as governor, was lost on no one.

“It’s been a really interesting week in British and royal diplomacy,” said Ed Owens, a royal historian. “People have talked about how this royal family has become a secret weapon for British diplomacy. We saw Keir Starmer wielding the king and the monarchy as such in his interactions with Trump.”

Mr. Owens said Mr. Trump’s well-established affection for the king and the royal family was an intangible factor that could stick in the back of the American president’s mind as he deals with Britain over Ukraine. Mr. Starmer has positioned himself as a bridge between Europe and the United States on the issue. And the president was plainly delighted by the invitation from Charles.

“A beautiful man, a wonderful man,” a beaming Mr. Trump told Mr. Starmer, from the same chair where he sat 24 hours later, as he chastised Mr. Zelensky, telling the Ukrainian president: “Don’t tell us what we’re going to feel. You’re in no position to dictate that.”

Buckingham Palace declined to comment on the status of the invitation to Mr. Trump, noting that the government is in charge of such issues. Mr. Starmer brushed aside calls for the visit to be canceled on Sunday, saying in a BBC interview that critics were “trying to ramp up the rhetoric without really appreciating what is the single most important thing at stake here — we’re talking about peace in Europe.”

Two people with knowledge of the palace said it was highly unlikely that the invitation would be rescinded, given the ill will that would generate with the White House — though the challenge of matching the calendars of two heads of state could mean that the state visit does not take place for months, they added.

In his letter, the king broached the idea of Mr. Trump first seeing him in Scotland, where the president has a golf club, Trump Turnberry, and Charles has a castle, Balmoral, to make the arrangements for the state visit at a later time. The Scotland meeting would be more informal, without the honor guard and lavish banquet in Buckingham Palace that Mr. Trump enjoyed in his last state visit in 2019.

“The idea of it being indefinitely delayed until a peace agreement is reached, on terms that are acceptable to Ukraine and Europe, is interesting,” Mr. Owens said, adding that the royal family “has bought Britain influence within these negotiations that it might not have had otherwise.”

For all his adherence to the monarch’s nonpolitical role, Charles is known to be more politically aware and opinionated than his late mother, Queen Elizabeth II. Early in his reign, he came under criticism for welcoming the president of the European Commission, Ursula von der Leyen, to Windsor Castle, after she signed a deal on Northern Ireland with Rishi Sunak, who was then Britain’s prime minister.

Critics saw it as putting a royal imprimatur on the government’s deal. They said that Charles, whose support of the European Union was well documented, had allowed himself to be used by Downing Street.

The king has been demonstrative in his backing of Ukraine, issuing statements and making regular visits to relief organizations that help refugees from the war. Early in the conflict, when he was still Prince of Wales, he visited a group in London and spoke to a family that had been evacuated from Kharkiv, in eastern Ukraine.

“So, what do you think the aim of the Russians is?” Charles asked them. “Is it to remove people?”

Given the king’s strong feelings and the delicacy of the moment, royal watchers said the government should be careful not to overextend what has so far been a beneficial role. His value as an agent of British “soft power,” they say, resides in his being above politics.

Even his long-planned visit to the aircraft carrier was symbolic, given Britain’s pledge to deploy troops to a peacekeeping force for Ukraine. The H.M.S. Prince of Wales is in training exercises before deploying on an eight-month mission to Asia.

Speaking to crew members in his dress uniform, Charles could have been addressing Mr. Starmer, a relatively new prime minister, who has been struggling to calm the tempest between Ukraine and the United States.

“Your deployment in the next month comes amidst new challenges in an ever-changing and more unpredictable world,” the king said. “It will undoubtedly demand tenacity and determination, both at sea and for those you leave behind at home.”