Washington is fortifying both military and diplomatic defenses in the Indo-Pacific in anticipation of a possible new era in American foreign policy after President Biden leaves the White House in January.

Whoever succeeds him, Mr. Biden’s highest lieutenants have been busy in recent days making sure the military-diplomatic structure built up during his administration will hold firm in the face of rising threats from America’s worst foes and pressure on the home front to pull back from alliances heretofore deemed vital to American security. 

It was with that goal in mind that Defense Secretary Austin and the defense ministers of Japan and Korea,  holding their first trilateral meeting in Tokyo, agreed to work more closely on sharing intelligence information and staging exercises. Japan’s defense minister, Minoru Kihara, discreetly noted  “changes in international circumstances,” as reported by Kyodo, the Japanese news agency.

The most visible immediate aspect of the tightening was the agreement to change the U.S. Forces Japan headquarters to a “joint force headquarters” in which all three countries would share command responsibilities.

 “The latest development also came as closer alignment between Russia and China, as well as with North Korea, has been seen amid Russia’s war on Ukraine,” said Kyodo. “The U.S. presidential election in November is closely watched as to whether Donald Trump, a critic of long-standing alliances, will return to the White House.”

Mr. Austin described the establishment of a new American-Japan headquarters as “the most significant change to U.S. Forces Japan since its creation” and promised “expanded missions and operational responsibilities … .to deter and respond to coercive behavior in the Indo-Pacific and beyond.”

The deal for tightened defense cooperation, a follow-up to the trilateral summit convened by Mr. Biden at Camp David last August including Japan’s prime minister, Fumio Kishida, and South Korea’s president, Yoon Seok-yul, avoided the term “alliance.” South Korea and Japan, both allied to Washington, still cannot bear the idea of a formal alliance with each other after 35 years of harsh Japanese rule over Korea that ended with Japan’s surrender at the close of World War II in 1945. 

Mr. Austin indicated Washington would be primarily responsible for making the trilateral relationship work as a de facto alliance.  Washington, he said, would “have a direct leadership role in planning and leading U.S. forces in both peacetime and in potential crises….to ensure greater peace and stability.” 

The Japanese capital was also the setting for another equally portentous meeting intended to bring America’s friends and allies together in common cause. The day after the defense ministers’ meeting. Secretary of State Antony Blinken was also in Tokyo bucking up diplomatic support from what’s called “The  Quad” — the informal, non-military grouping of America, Australia, Japan, and India. 

The meeting wound up with a statement in which all four decried China’s claims to the South China Sea and the straits  between Taiwan and the Chinese mainland without criticizing China directly. Similarly, the Quad, in their final joint statement, denounced North Korea’s “malicious cyber activity” and “weapons of mass destruction” but said not a word about Russia, to which North Korea is shipping artillery shells and other munitions in return for Russian food, oil and technological expertise on missiles. 

It’s been a busy few days for Mr. Blinken. Before going to Tokyo, he met China’s foreign minister, Wang Yi, on the sidelines of a meeting of ministers of the Association of Southeast Asian Nations at Vientiane in Laos. To no avail, Mr. Blinken pressed the case for “a free and open Indo-Pacific” and complained about China’s “coercive and intimidating maneuvers in the South China Sea.”

Mr. Wang’s response showed the futility of the discussion, advising that Mr. Blinken, in the words of China’s foreign ministry, “not take any more action to fan the flames, stir up trouble, or undermine maritime stability.”