At noon on Thursday, July 17th, Vice-President Joe Biden was on his way to Detroit for a day of light political fare: a fund-raiser, a community-college visit, a speech to progressive groups. Shortly before he landed, an aide told him that Malaysia Airlines Flight 17, en route from Amsterdam to Kuala Lumpur, had crashed in eastern Ukraine, an area controlled by pro-Russian separatists. Details were sketchy, but intelligence suggested that the Boeing 777-200, carrying two hundred and ninety-eight people, had been hit by a surface-to-air missile. There were no survivors. When Biden reached the dais at a convention center in Detroit, he said that the plane “apparently has been shot down.” He added, “Not an accident. Blown out of the sky.”

Of all the foreign crises confronting the White House, none has consumed more of Biden’s time and attention in recent months than the wars in Ukraine and Iraq. A former chairman of the Senate Committee on Foreign Relations, he has been visiting Eastern Europe since the nineteen-seventies, and he was tapped to be Barack Obama’s running mate in 2008 partly to compensate for the candidate’s inexperience abroad. Last year, Biden said that the President “sends me to places that he doesn’t want to go.”

After more than five years in the White House, Obama leans less visibly on Biden for foreign-policy advice than he once did, but Biden remains so closely identified with the Administration’s handling of the most vexing national-security problems that, when militants seized large parts of Iraq, in June, Mitt Romney told a mostly Republican audience that the “Obama-Biden-Hillary Clinton foreign policy” was to blame. The trials facing the President and the Vice-President, who are separated by nineteen years and a canyon in style, have brought them closer than many expected—not least of all themselves. John Marttila, one of Biden’s political advisers, told me, “Joe and Barack were having lunch, and Obama said to Biden, ‘You and I are becoming good friends! I find that very surprising.’ And Joe says, ‘You’re fucking surprised!’ ”

Last November, Ukraine’s President Viktor Yanukovych scrapped an agreement with the European Union, triggering protests that plunged the country into crisis. Biden had known Yanukovych since 2009 and struck up a towel-snapping rapport. “He was gregarious,” Biden told me earlier this year. “I said, ‘You look like a thug!’ I said, ‘You’re so damn big.’ ” As the crisis escalated, Biden spoke with Yanukovych by phone nine times, urging him to reconcile with the demonstrators. But on February 20th government snipers opened fire on protesters, killing at least eighty-eight people in forty-eight hours. Yanukovych fled, leaving his subjects to pry open his mansion and find the fruits of his kleptocracy: pet peacocks, a fleet of antique cars, a private restaurant in the shape of a pirate ship. In the aftermath, Russian forces swept into Crimea, and Vladimir Putin christened it Russian soil.

On Easter Sunday, Biden boarded Air Force Two, bound for Kiev, the beleaguered Ukrainian capital. Compared with the Commander-in-Chief, the Vice-President flies in restrained splendor. The modified Boeing 757 was well used. An armrest came off in a passenger’s hands. The Vice-President had a private cabin with a foldout bed, a desk, and a guest chair, but if a second visitor arrived a plastic cooler passed as a seat. “If you want the trappings, it’s a hell of a lot better to go into some other line of work,” Biden said.

Biden’s mission was short and specific: two months had passed since Yanukovych fled, and the arrival of America’s second-highest-ranking official was intended to reassure Ukraine’s fragile government, and deter Putin from moving deeper into Ukrainian territory.

Air Force Two touched down in Kiev, a city with gracious boulevards, chestnut trees, and so many domed churches that the Bolsheviks declared it unfit to be a Communist capital. The fighting in the city was finished, but the Maidan encampment, which had been the center of protests, still resembled a set for “Les Misérables”: tall, jagged barricades of metal, timber, and tires marked the battle lines. Sparks rose from open-air fires. In one of the few signs of recovery, the cobblestones that had been pried up to hurl at the police were stacked and ready for repaving.

At the parliament, a Stalin-era building with a colonnaded entrance, Biden was ushered in to see a group of politicians who were vying to lead the new government. After so many years, he has an arsenal of opening lines that he can deploy in Baghdad, Beijing, or Wilmington. One of his favorites: “If I had hair like yours, I’d be President.” He also adapts his routine to fit the circumstances. In Kiev, he approached Vitali Klitschko, a six-foot-seven former heavyweight boxing champion who was known as Dr. Ironfist before he entered politics. Biden peered up and clenched Klitschko’s right biceps. Moving down the table, he met Petro Poroshenko, a Presidential candidate and billionaire who had made his fortune in the candy business. Biden, who is considering a long-shot run for the Presidency in 2016, told the group, “I’ve twice been a Presidential candidate and I hope you do better than I did.” (The next month, Poroshenko won the Presidency.)

Biden took his seat at the head of the table. When he was thirty years old, he became one of the youngest senators in history, and he has parted with youth begrudgingly. His smile has been rejuvenated to such a gleam that it inspired a popular tweet during the last campaign: “Biden’s teeth are so white they’re voting for Romney.” At seventy-one, with his hairline reforested and his forehead looking becalmed, Biden projects the glow of a grandfather just back from the gym, which is often the case. (On Inauguration Day in 2017, Biden will be seventy-four, three months older than Ronald Reagan was at the start of his second term. Hillary Clinton will be sixty-nine.)

For his hosts in Kiev, the Vice-President had only a small aid package to announce: fifty-eight million dollars in election help, energy expertise, and non-lethal security equipment, including radios for the border patrol. More important, Biden wanted to convey a message to the new leaders in Kiev that regaining legitimacy would require changes beyond just resisting Russian interference. On the 2013 corruption index produced by Transparency International, Ukraine was ranked No. 144, tied with the Central African Republic, out of a hundred and seventy-seven countries. Biden told those seated around him, “To be very blunt about it, and this is a delicate thing to say to a group of leaders in their house of parliament, but you have to fight the cancer of corruption that is endemic in your system right now.” Biden likes to be candid in such settings. In 1979, on one of his first trips to the Soviet Union, he listened to an argument from his Soviet counterpart, and replied, “Where I come from, we have a saying: You can’t shit a shitter.” Bill Bradley, then a fellow-senator on the delegation, later asked the American interpreter how he had translated Biden’s comment into Russian. “Not literally,” the interpreter said.

Over the years, Biden has acquired a singular place in the pop culture of American politics. In a White House that privileges self-containment, Biden ambles between exuberant and self-defeating. He was barely in the West Wing before the Onion declared, in a headline, “SHIRTLESS BIDEN WASHES TRANS AM IN WHITE HOUSE DRIVEWAY,” establishing a theme—“Amtrak Joe,” the hell-raiser at the end of the bar—that is so enduring that it obscures the fact that he is a lifelong teetotaller. (Too many alcoholics in his family, he says. He grew up sharing a room with his mother’s brother, and recalled of the experience, “Even as kids, we noticed Uncle Boo-Boo drank a bit heavily.”)