Washington ? As he flew to Yokohama, Japan, earlier this month, President Barack Obama was unknowingly on the way to the sleeper event of the fall, a peripheral get-together almost entirely overlooked in a battery of colossal global summits.

Hardly anyone outside the White House even knew of the one-on-one with the Russian president, quietly scheduled for that Sunday morning two weeks ago.

And even the president’s team didn’t realize Obama and Dmitry Medvedev were on the brink of a deal that could eventually bring the Russians in on a plan to build a missile defense system in Europe — in cooperation with the treaty organization whose longtime mission was to keep the Russian nuclear threat in check.

For weeks, Russian negotiators had been putting the brakes on missile talks. One top Obama adviser was ready to drop back on it for at least a year.

But it was to be a lesson in summitry for a White House entourage — officials, advisers and journalists — that was focused on the big-name, acronym summits dominating November. Especially stinging for Obama was the failure to achieve its key objectives at the G20 summit of industrialized nations in Seoul, South Korea, leaving the U.S. to go it alone in dealing with its fragile economy and high unemployment.

In the realm of diplomacy, though, deals that seem entirely on track fall apart when the titans convene. And newer, more significant ones can appear magically out of thin air.

“It’s interesting,” deputy national security adviser Ben Rhodes said in retrospect, “how a bilateral meeting at one summit is necessary to yield results at another.”

Aboard Air Force One on the way to Yokohama, the president shook off the headlines that had irritated him in Seoul.

Such meetings don’t always produce “revolutionary progress,” he said, but rather “evolutionary progress.”

The next weekend in Japan, Nov. 13 and 14, was devoted almost entirely to the Asia-Pacific Economic Cooperation summit. The side-meeting there with Medvedev on Sunday morning was expected to be just another meet-up in a long run of them for the two forty-something lawyers.

The presidents and their top advisers arranged themselves around a long table in a small meeting room of the InterContinental Yokohama Grand Hotel, and started talking about previously negotiated items — Afghanistan, trade, the START arms treaty they’d signed but not ratified.

On missile defense, Obama knew the negotiators in Brussels had not worked out the important issues, like how to agree on common threats or resume joint defense exercises.

He turned the conversation there anyway. As he did, advisers in the room with him were surprised by Medvedev’s demeanor.

“He was leaving himself wiggle room,” said one senior administration official who was there, “and not committing to anything. But he was clearly very friendly and open to what the president was saying.”