Japanese Prime Minister Fumio Kishida may not have foreseen standing amicably together with South Korean President Yoon Suk Yeol at the U.S. presidential retreat of Camp David quite so quickly when they first held formal talks in Tokyo just five months ago.
But whether this was truly a historic event will not likely be determined for some time to come.
What is clear is that U.S. President Joe Biden chose to host the trilateral summit at a symbolic location and that the three leaders unveiled a host of new initiatives to prevent the current positive momentum in their ties from going backward.
The agreements included pledges to meet at least once a year, either by arranging further standalone summits or by taking advantage of opportunities to gather on the fringes of larger multilateral events.
"If I seem like I'm happy, it's because I am," Biden said Friday at the outset of a joint press conference in concluding the daylong summit with Kishida and Yoon. "We meet in this historic place to make a historic moment. And I believe that to be true."
Camp David, though situated not far from Washington, is nestled in the mountains and not accessible to the public. It has served for decades as an ideal location for U.S. presidents to work and host foreign leaders in a tranquil atmosphere.
In preparing a more intimate setting than the White House, Biden's primary goal was to make sure that the three-way cooperation with Washington's major Asian allies will be sustained in the years to come, regardless of changes of government or domestic political issues.
Jeffrey Hornung, a senior political scientist at the Rand Corporation think tank, said the rapidly improving ties between Japan and South Korea after years of bitter disagreements over wartime issues is a "big feather in the (Biden) administration's hat."
Along with many other pundits and policymakers, Hornung believes Biden's decision to select the rustic retreat as the first standalone summit's venue created a necessary "Venn diagram" in which the leaders could work together on common ground before moving to the next phase.
He said it was important for leaders to have heart-to-heart conversations, expressing willingness to work with each other but understanding each other's limits.
But Hornung, who specializes in East Asian security affairs at the U.S. institute, noted that while issues concerning North Korea that the leaders agreed on are "low-hanging fruit," many difficult issues will likely stand in their way as they go forward.
Even if they start sharing real-time data about North Korean missile launches by the end of this year as agreed, he said, it is not realistic for the armed forces of Japan and South Korea to respond together to them in the foreseeable future.
As Tokyo and Seoul do not have a security alliance and share a bitter past that includes Japan's 1910-1945 colonization of the Korean Peninsula, Japanese officials involved in drafting some of the statements for the summit said they were careful about the wording of the documents.
The Biden administration had pushed the idea of "institutionalizing" the trilateral cooperation in an attempt to make their framework more durable, but that, as well as phrases and words repeatedly used by senior U.S. officials in the run-up to the summit such as the establishment of a "hotline" and "contingency," were not included in the statements.
One of the Japanese officials, who spoke on condition of anonymity, suggested that Tokyo was reluctant to employ any word that might give the impression that the trilateral framework would develop into a security alliance, noting that some remarks from the U.S. side exceeded what had been agreed.
Biden, Kishida and Yoon also discussed shared concerns about China's actions that run counter to the rules-based international order and touched on its "dangerous and aggressive behavior" in the South China Sea.
Nicholas Szechenyi, deputy director for Asia at the Center for Strategic and International Studies, said strengthening the trilateral relationship would be "effective" against China, which accuses the United States of trying to gradually form a "mini NATO" in Asia.
"If China didn't care and didn't respond, it would mean that it didn't have an impact. This complicates Chinese strategy," Szechenyi said.
He said he is also "optimistic about the durability of this framework because I think both Japan and South Korea agree that the security environment in Northeast Asia is deteriorating rapidly," citing the threats posed by Chinese coercion and North Korea's ballistic missile and nuclear weapons programs.
"So they have no choice but to strengthen their own defense capabilities, improve the relationship with each other and strengthen coordination with the United States," he said.
A senior Biden administration official said, "Nothing in life is absolutely irreversible."
But the official, who declined to be named, said the chance of a future U.S. president altering the trilateral engagement is slim as enhancing Washington's alliances and partnerships is largely supported by the mainstream of the Democratic and Republican parties.
"I personally have rarely experienced this much bipartisan agreement on any initiative," he said.