Many observers in Japan—and some hawks in the United States—wanted to see Biden draw a red line in Beijing over China’s ADIZ and demand it be revoked (Japan, South Korea, and the United States all maintain ADIZs around their own shores). But they were disappointed.

Japan's prime minister, on the other hand, had a shrewder understanding of the geopolitics at play in the dispute. In a carefully constructed diplomatic effort, Abe did not ask Biden to call for a rollback of China’s ADIZ because, according to a senior official in Japan’s Ministry of Foreign Affairs, Abe knew that Biden would not make that request of Xi Jinping, and didn't want the world to see any light between Japan and America on the issue.

Why wouldn't Biden demand that the Chinese step back from a move that senior administration officials have called “potentially dangerous” and “provocative”? Insiders say the vice president and President Obama didn’t want to draw a red line in an already-tense mess when there are options beyond escalating it into a full-blown conflict—and especially when China would likely balk at such a demand.

So into the fray Biden has moved, counseling all parties to contribute to regional stability rather than undermining it and harming their own economic prospects and security. On Tuesday, Biden reaffirmed America’s support of Japan, calling the island nation the “cornerstone” of America’s security in the Pacific. He expressed support for a Japanese call to create a hotline between Tokyo and Beijing and broadened the initiative conceptually to include regional crisis management mechanisms and infrastructure, ostensibly bringing South Korea into the mix to preempt “accidents and miscalculations.”

While in Tokyo, Biden called on China to not create more ADIZs and to keep Chinese fighter jets from intercepting other aircraft. White House officials reported that the U.S. and Japan will not recognize China’s ADIZ and will not share flight identification information with China for U.S. and Japanese military aircraft (commercial aircraft are managed differently than fighters and bombers, and the Federal Aviation Administration automatically issues guidance to all commercial carriers operating in international airspace to comply with information requests in air defense identification zones). Senior Obama administration officials have stated that while commercial U.S. aircraft will provide Chinese authorities with their flight information, this does not represent a shift in policy or official recognition of China’s ADIZ.

When U.S. officials granted me and other journalists access to a portion of the meeting between Biden and Xi, the vice president seemed solemn, emphasizing the importance of his friendship with the Chinese president (the two have previously met in Chengdu and Los Angeles) and how a new approach to great power relations, which Xi has advocated, requires trust and understanding the motives of the other side.