America and the Philippines have opened a new chapter in their long and complicated relationship, and the Republic of China on Taiwan, for one, is vastly relieved.

No sooner had President Biden, standing beside the Philippine president, Ferdinand “Bongbong” Marcos Jr., at the White House, reaffirmed America’s “ironclad commitment to defending the Philippines” than Taiwan’s foreign ministry promised “to cooperate with the United States” to help “ensure peace, stability, and prosperity across the Taiwan Strait and the region.”

From South Korea and Japan through Taiwan to the Philippines — and beyond — Washington is building defenses against Communist China. Australia holds down the southern perimeter in a security pact named Aukus, for Australia, the United Kingdom and the United States. Australia and America also are members of the Quad Four, an informal grouping in which they share common cause with India and Japan.

Mr. Biden, overlooking the history of America’s role in deposing the corrupt dictator Ferdinand Marcos Sr. in the People Power Revolution of 1986, told Mr. Marcos Jr.,  “I can’t think of any better partner to have than you.”

Those words were if anything more effusive than the welcome Mr. Biden had given a few days earlier to South Korea’s president, Yoon Suk-yeol, on an elaborate state visit to Washington. That mission culminated in the vague promise of “extended deterrence,” including America’s “nuclear umbrella,” for defense against the rising menace of North Korea’s nukes and missiles.

Conspicuously, Messrs. Biden and Marcos omitted any mention of South Korea, which hesitates to endorse a strong policy against China, by far its biggest trading partner. China exerts power and influence over North Korea by providing the North with all its oil and half its food while presumably dissuading the strongman leader, Kim Jong-un, from firing missiles laden with tactical nuclear warheads against South Korea.

Unlike South Korea’s modern military establishment, the Philippines’ dilapidated armed forces are notoriously short of aircraft, armored vehicles, and much else. They cannot possibly match China’s build-up in the South China Sea, virtually all of which China claims as Chinese territory, but the inference was America would come to the rescue of a nation that once harbored America’s largest air and naval bases.

Adding substance to words, the White House said America was sending three C-130 transport planes and two Coast Guard patrol vessels to the Philippines. They will hardly begin to match the power of China, which has built an airstrip on Mischief Reef in the South China Sea and regularly sends planes and ships on patrol.

Mr. Biden promised the same level of defense for the Philippines as for Korea and Taiwan, including “unwavering commitment to freedom of navigation and overflight in the South China Sea” as more than 17,000 American and Filipino troops wrapped up their biggest exercises in years. Americans will go on moving in and out of Philippine bases where the Philippines has agreed they can store gear for exercises — or war.

It was the reference to Taiwan in the joint statement issued by the two presidents that most heartened leaders of Taiwan, bound closely to America even though Washington and Taipei have not had diplomatic relations since President Carter broke off with Taipei in 1978 and recognized Beijing as the capital of one China.

Washington, selling arms to Taiwan, pursues “strategic ambiguity” in the face of  Chinese threats to recover the independent island democracy by force. Taiwan’s foreign ministry opened its statement by noting that Messrs. Biden and Marcos had reaffirmed “the importance of maintaining peace and stability across the Taiwan Strait as an indispensable element of global security and prosperity.” 

Understating the emotional appeal of that reference, the ministry said “the Republic of China (Taiwan) welcomes and appreciates this statement.” China, it went on, ”has repeatedly and unjustifiably escalated coercion and military intimidation against Taiwan, posing a serious challenge to regional security and stability and eliciting a high level of concern from the international community.” 

Beijing heaped derision on the show of rapport between Messrs. Biden and Marcos, who has reversed the pro-China policy of his predecessor, Rodrigo Duterte. While downplaying Philippine ties to America, Mr. Duterte courted China as the most powerful country in the region and questioned if America would be willing to defend the Philippines in a showdown. 

“By hyping S. China Sea issues, Taiwan question, Washington locks up Philippines into its anti-China fleet,” the Global Times, published by the Communist Party’s People’s Daily at Beijing, said in a headline. America “is forcing the Philippines to sacrifice its own independence to serve for the US’ Indo-Pacific strategy.” 

The article quoted a professor at China Foreign Affairs university, Li Haidong, as saying the Philippines had been coerced by Washington after having “reiterated its unwillingness to choose sides between China and the U.S. given its close relations and trade with China.” 

Xinhua, the Chinese news agency, gleefully reported that “Philippine fishermen groups and their sympathizers” are protesting “the live-fire sea drills involving the sinking of a decommissioned navy ship,” a highlight of the exercises. 

Above the report was a large photograph of a demonstrator holding a sign saying, “U.S. Troops Out Now.” The article, of course, did not mention frequent protests by the Philippines against Chinese harassment and interdiction of Philippine fishing boats. 

Messrs. Biden and Marcos, in their joint statement, said they “support the right and ability of Filipino fisherfolk to pursue their traditional livelihoods.” 

It was not likely, though, that America’s commitment extended to defense of fishing boats. Nor was it certain what a few Philippine patrol boats, including those donated by the Americans, could do in defending the long coastlines of the country’s 8,000 islands.

Beside modernizing the Philippines’ feeble military establishment, racked by corruption and the need to repress internal Communist and Muslim revolts, Mr. Biden said “we’re deepening our economic cooperation,” beginning with a trade mission in an effort to revitalize two-way commerce.

Mr. Biden played on the ties that bind America to the Philippines, taken over as a colony in the Spanish-American War of 1898, held for more than three years by Japan in World War II, and granted independence after the war. Washington had to close its Clark Air Base north of Manila and the American Navy base at Subic Bay on the South China Sea in 1992 after the Philippine senate refused to renew the lease.

Emotional, cultural, and linguistic bonds are more difficult to break. “Our countries not only share a strong partnership,” as Mr. Biden observed, “we share a deep friendship — one that has been enriched by millions of Filipino Americans in the communities all across the United States of America.”