He talked dinosaurs with the British prime minister's sons and bonded with the young Russian president over their shared coming of age in the post-Cold War years. He elicited an embrace from the physically standoffish leader of Turkey.
At one point in President Obama's overseas charm offensive, one world leader confided that he'd never felt able to personally "connect" with the previous American president.
"You'll notice my approach is quite different from my predecessor," Obama told the prime minister of Spain, as the two began and ended an official bilateral meeting by talking about their daughters.
As Obama hugged his way across Europe and Turkey in recent days, the visual images clearly showed a president trying hard to build personal relationships with his foreign counterparts. In one week's time, he sat down with the leaders of 15 countries.
But amid the photo opportunities and public displays of affection there emerged a clarifying message about dealings based on "shared interests."
Rapport is "necessary but also not sufficient," said Denis McDonough, Obama's deputy national security advisor.
"A personal relationship without a sound grounding of what our national interest is is nice but, at the end of the day, inconsequential," McDonough said. "A strong personal relationship with a solid understanding of what our national security interest is, and what our desired end state and goal should be, is the kind of form that with the proper substance ends up advancing U.S. interests."
The early score card doesn't immediately vindicate the approach. Obama returned home Wednesday with commitments from other nations to spur the global economy through government spending, but they are smaller than the U.S. wanted. Nor did leaders rush to send new combat troops to Afghanistan to support the mission there.
Obama's team says it's too early to judge, though.
"Over time, the seeds that were planted here are going to be very, very valuable for the security and progress of the United States," senior advisor David Axelrod said as the trip drew to a close.
Obama faced a "greatly diminished curve of lowered expectations" of what he could accomplish going into the trip, said Steven Schrage, international business expert at the Center for Strategic and International Studies, a nonpartisan think tank in Washington. "Grading on that curve, because the challenges were so great, he did handle the diplomatic matters well."
Guiding his interactions was a new philosophy the White House began to reveal over the week, one that differs in one significant way from the previous administration's.
Former President George W. Bush acknowledged strong personal feelings for other world leaders, saying after his first meeting with then-Russian President Vladimir Putin, in 2001, that he had gotten a "sense of his soul" by peering into his eyes. With countries that crossed the administration on one issue -- Iraq, for example -- bilateral relations in general seemed to go south.
Obama's White House consistently offered analysis during the trip based not on how he clicked personally with other leaders but on where their interests aligned. The phrases "shared interest" and "shared challenges" cropped up in at least a dozen post-meeting analyses by staffers traveling with the president.
Obama and Russian President Dmitry Medvedev reached an agreement to move toward reduction of nuclear arms not because they liked each other but because it's in their countries' mutual interest to do so, said one senior administration official after that meeting at Obama's guest house in London.
Obama brought up human rights with Chinese President Hu Jintao, said another aide, but the pair then moved on to the economy, an area of greater mutual concern.
And in a news conference in London, Obama dispassionately explained that he cares about the health of the world economy because American "self-interest" is inextricably linked to it.
"Look, I'm the president of the United States," Obama told a Chinese journalist. "I have a direct responsibility to my constituents to make their lives better."
In an era of "integration and interdependence," he said, his personal effectiveness involves "providing Americans insight into how their self-interest is tied up with yours."
Yet even as Obama openly embraced that pragmatic message, he -- and his wife -- embraced leaders, literally. First Lady Michelle Obama caused a stir in Britain when she slipped a bare arm around Queen Elizabeth II in a rare royal hug.
The Turkish news media took note of Prime Minister Recep Tayyip Erdogan's hug of Obama.
In his private meeting with Spanish Prime Minister Jose Luis Rodriguez Zapatero, Obama slipped in a few Spanish words, at one point describing the leader as "simpatico," according to a Spanish speaker who was in the room.
When the president and other members of the Group of 20 met for an economic summit in London, there was a notable personal moment as they were lining up for a photo.
Canadian Prime Minister Stephen Harper stepped out at just the wrong moment to speak with an aide, and returned as the group was breaking up.
"The president asked everybody to get back together," said a White House official who was there, "so they could take it again."
"I think personal chemistry does matter," said Stephen Flanagan, the Henry A. Kissinger chair at the Center for Strategic and International Studies.
Examples include the warm personal relationships that bound President George H.W. Bush and Soviet President Mikhail S. Gorbachev and Secretary of State James A. Baker III and Soviet Foreign Minister Eduard Shevardnadze.
"It helped ease the end of the Cold War and secure the peaceful unification of Germany," Flanagan said.
Important as that chemistry might be, he said, it can achieve only so much. "It cannot overcome strong policy differences," he said, "but it can sometimes make difficult decisions easier to pursue."