WASHINGTON — After Russia invaded Ukraine last year, President Biden reflected privately on his long-distance conversations with President Volodymyr Zelensky. He did not know the man well — and might never get to. It was chilling, several people remember him observing grimly, to think that he might be talking with a dead man.
Mr. Biden was hardly the only one to assume that Mr. Zelensky might not survive the Russian onslaught, given the target the Kremlin had put on his back. But the American president was happy to be proved wrong — and surprised to discover, like the rest of the world, that Mr. Zelensky was more than a former comedian and tougher than anyone imagined.
By the time Mr. Biden made a dramatic unannounced visit to wartime Kyiv this week, the two had grown close enough to greet each other with the easy familiarity of old friends. “How are the children?” Mr. Biden asked. “It’s amazing to see you,” he added, perhaps still shocked that the Ukrainian president has escaped Russian efforts to kill him. Mr. Zelensky inquired about Jill Biden. “She’s doing well,” the president replied. “She’s still teaching.”
It has not always been so convivial. The two leaders have been on a remarkable journey together since the invasion one year ago on Friday, forging a partnership that is critical to the future of the international order but that at times has been fraught with friction, according to officials in both camps who asked not to be identified. Mr. Biden has secured $113 billion in military and other aid to be delivered to Ukraine, but in their telephone calls it has never been enough for Mr. Zelensky, who presses for more, more, more, faster, faster, faster. It took months to develop a better understanding of each other and smooth over hard feelings.
It is, after all, a relationship of necessity but not of equals, one of mutual interests but disparate priorities. If Mr. Zelensky is a modern-day Winston Churchill, as admirers often say, then Mr. Biden finds himself assigned the role of Franklin D. Roosevelt before Pearl Harbor, mustering the so-called Arsenal of Democracy to arm European allies without drawing the United States directly into a war.
While Mr. Biden shares Mr. Zelensky’s goal of driving out Russian invaders, he worries about provoking President Vladimir V. Putin into escalating the war beyond Ukraine’s borders or into a nuclear conflict. Mr. Biden’s reluctance to provide the most advanced weaponry vexes Mr. Zelensky, but the Ukrainian has learned how to slowly wear down resistance to eventually get much of what he wants.
“Both are really determined and strong leaders,” said Igor Novikov, a former adviser to Mr. Zelensky on American affairs. “When their interests align, it’s the best relationship ever. If there are misunderstandings or different points of view, emotions pop up. I classify it as a complicated relationship, not in the bad sense. But it’s complicated.”
The tension is inherent to their different positions and responsibilities. “There’s just a basic structural thing here that has nothing to do with the personalities of Biden or Zelensky,” said Michael A. McFaul, an ambassador to Russia under President Barack Obama who is regularly in touch with Ukrainian leaders.
“Zelensky is trying to save his country,” Mr. McFaul said. “There’s nothing worse than getting the reports at the end of the day about how many people have died. Nobody should be surprised that he wants more all the time. He believes, and I think he’s right, that this is the way this war ends.”
As for the American president, Mr. McFaul said, “Biden feels, rightly so, that he’s mobilized the world and he’s mobilized America and the Pentagon has done more than it’s ever done before, and he’s frustrated he doesn’t get more praise for that.”
As wartime allies go, Mr. Biden and Mr. Zelensky are a historical odd couple, an 80-year-old career politician who became a pillar of his country’s political establishment and a 45-year-old satirist who once played a president on television but had never served in public office before being elected to lead his nation. Mr. Biden came of age during the Cold War and was first sworn into the Senate five years before Mr. Zelensky was born. Mr. Zelensky was 13 when his country emerged from the collapsing Soviet Union as an independent country.
Their relationship was burdened before they ever met. Shortly after Mr. Zelensky was elected in 2019, President Donald J. Trump pressured him to investigate Mr. Biden, a demand that led to impeachment. New to government, Mr. Zelensky felt burned, assuming the byzantine maneuvering was the norm for American politics and wary of where it left him when Mr. Biden defeated Mr. Trump.
It did not go unnoticed in Kyiv that Mr. Biden spoke by phone with Mr. Putin in January 2021, just six days after taking office, while Mr. Zelensky did not get a call until April. Mr. Biden did not even nominate an ambassador to Ukraine until a year later, two months after the Russian invasion. In summer 2021, while Mr. Biden met with Mr. Putin in Geneva, the Ukrainians lashed out at visiting American officials for not imposing sanctions on Germany over its new Nord Stream 2 pipeline with Russia.
By winter, as Russian troops gathered on the Ukrainian border and American intelligence concluded that Mr. Putin planned to invade, Mr. Zelensky remained skeptical of Mr. Biden’s public warnings.
When the Ukrainian leader decided to travel to the Munich Security Conference last February, Mr. Biden’s team advised him not to leave his country in case it was attacked. He attended anyway, rallying international support and returning before the invasion.
How Times reporters cover politics. We rely on our journalists to be independent observers. So while Times staff members may vote, they are not allowed to endorse or campaign for candidates or political causes. This includes participating in marches or rallies in support of a movement or giving money to, or raising money for, any political candidate or election cause.
Biden administration officials privately also pressed Mr. Zelensky to develop a succession plan in case something happened to him because the Ukrainian Constitution only called for the speaker of Parliament to fill a vacancy and listed no one else in line.
On the night of the invasion, Mr. Biden and Mr. Zelensky spoke by telephone. It was a harrowing moment for the young Ukrainian, who was in a capital facing a brutal assault. During his visit to Ukraine this week, Mr. Biden recounted their conversation.
“You told me that you could hear the explosions in the background,” Mr. Biden recalled. “I’ll never forget that. And the world was about to change. I remember it vividly, because I asked you — I asked you next — I asked you: ‘What is there, Mr. President? What can I do for you? How can I be of help?’ And I don’t know that you remember what you said to me, but you said, and I quote: ‘Gather the leaders of the world. Ask them to support Ukraine.’”
“And you said that you didn’t know when we’d be able to speak again,” Mr. Biden continued. “That dark night, one year ago, the world was literally, at the time, bracing for the fall of Kyiv — it seems like a lot longer ago than a year, but think back to that year — perhaps even the end of Ukraine.”
The Biden team assumed that Mr. Zelensky would either be killed or lead a government in exile. But clad in an olive green sweatshirt, he refused suggestions to leave Kyiv, angry that the Americans doubted Ukraine’s resolve.
Ukrainian officials spread the story that Mr. Zelensky rebuffed the suggestion with a memorable quote: “I need ammunition, not a ride.” The Biden team considers the story apocryphal, a former administration official said, but was impressed by the mythmaking, which is a common tool of war.
Less than a week after the invasion, Mr. Biden told television anchors at an off-the-record lunch that he saw no offramp to get Mr. Putin to stop. He said he believed Russia would be able to defeat Ukraine, taking major cities, and he expected many people to die, according to an account from in the room. The idea that Ukraine could beat the Russians “is not going to happen,” Mr. Biden said. He acknowledged that to occupy and control the country was a more daunting challenge, but believed that Mr. Putin’s only game plan was to topple Mr. Zelensky and set up a puppet government.
The assumption that Moscow would quickly win influenced a strategic decision by Mr. Biden that proved an enduring source of grievance with Mr. Zelensky. American officials feared sending sophisticated weaponry to Ukraine that might fall into Russian hands, much like in Afghanistan when Mr. Biden withdrew troops the previous year. So they were restrained in what they sent.
In what became regular conversations with Mr. Biden, however, Mr. Zelensky relentlessly pushed for more, often skipping lightly over the gratitude for what the Americans had provided and instead presenting a list of what they had not.
Mr. Biden bristled at the president of the United States being treated like a supply sergeant, according to administration officials, believing that such lists should be discussed by their aides while the two leaders focused on higher-level questions.
On at least one occasion last summer, as reported by NBC News, Mr. Biden lost his temper when he called to tell Mr. Zelensky about $1 billion in aid he had just approved only to have the Ukrainian leader immediately list what else he needed.
“Zelensky learned early on that it was a mistake not to provide the list,” Mr. McFaul said. “He learned that the best way to get the system to work was to give the list. And Biden didn’t like it, absolutely.”
Mr. Zelensky’s approach stemmed from living in a capital under regular bombardment. “In Zelensky’s view, the weapons deliveries are appreciated but extremely slow,” Mr. Novikov said. “For those delays, we are paying with Ukrainian blood.”
Biden administration officials appreciated the strain Mr. Zelensky was under.
“If I were in your position, I would be doing the exact same thing,” Mr. Biden would tell Mr. Zelensky, according to a senior official. In the early weeks of the war, the official said, Mr. Zelensky would sign off calls with Mr. Biden by saying, “This may be the last time I see you.”
But Biden officials privately appealed to Mr. Zelensky’s team to handle the phone calls differently. The situation improved once Bridget A. Brink, the new American ambassador, arrived last spring. And Mr. Biden has often given in to Mr. Zelensky, eventually agreeing to send HIMARS guided rocket launchers, a Patriot antimissile battery and M1 Abrams tanks, all of which he initially withheld.
The relationship has grown stronger in recent months. Mr. Zelensky’s splashy visit to Washington just before Christmas seemed to make an impression on Mr. Biden and his national security adviser, Jake Sullivan, who calls himself the quartermaster of the Ukraine war and works closely with Andriy Yermak, Mr. Zelensky’s top adviser. And Mr. Biden’s return trip to Kyiv highlighted their solidarity as Mr. Zelensky thanked him profusely for help that will be “remembered eternally,” while pressing for additional weapons more gently.
“At the beginning, it was a quite rocky relationship and there’s still a certain rockiness but less,” said John Herbst, a former American ambassador to Ukraine who has praised Mr. Biden for the aid but argues that it has been way too slow. “To this day, the administration still complains that the Ukrainians are ingrates — and that’s because they refuse to look critically at their own policy.”
Speaking by telephone from Kyiv, Mr. Herbst said Mr. Biden’s visit went a long way toward cementing the partnership with Mr. Zelensky — to a point. “I know the Ukrainians loved the visit,” he said. “Him being on the streets of Kyiv struck a real chord and demonstrated the support they wanted to see. But the elite are still asking, where’s the beef?”
Peter Baker reported from Washington, and Andrew E. Kramer from Kyiv, Ukraine. Katie Rogers contributed reporting from Washington.