How China’s Military Is Flexing Its Power in the Pacific

A look at how Beijing is pushing boundaries, and what the U.S. and its allies are doing in response.

HONG KONG—China’s military is extending its reach deeper into the Pacific, sending ships and aircraft into new territory in a push that has spurred the U.S. to strengthen defenses and alliances in the region.

How China’s Military Is Flexing Its Power in the Pacific

Beijing has long resented what it sees as interference by the U.S. and its allies in its traditional sphere of influence in the Asia-Pacific region. Now, it is asserting itself more aggressively in its backyard while also pushing well beyond longstanding geographical limits of its military.

In response, the U.S. and its allies are dispersing military assets more widely so that they can respond better in case of a clash with China. The U.S. is also pressing its Asian partners to bolster their own defenses.

Here is a look at how China’s military is pushing boundaries in the Pacific and how the U.S. seeks to respond to the perceived threat.

When two Chinese aircraft carriers performed joint exercises in the western Pacific in June, Chinese forces conducted more than 1,000 aircraft takeoffs and landings, and jet fighters twice tailed Japanese patrols that were monitoring the exercises, Japan said.

The U.S. has deployed so-called carrier-killer missiles in the northern Philippines, making it more dangerous for the Chinese to pass through the first island chain in a conflict. But the Chinese show of force in June was an important sign of defiance.

“The issue is not that they have increasing blue water capabilities and are deploying further from their coast—that’s to be expected,” said Jennifer Parker, an adjunct fellow in naval studies at the University of New South Wales Canberra. “The issue is the nature in which they are doing it, which is provocative.”

Similarly, a Chinese trip in February and March around Australia was seen as cause for concern. “Australia is not on its way to anywhere. If you send a naval task group to circumnavigate Australia, you’re doing it to prove a point,” said Parker.

In the U.S. view, the greatest menace in China’s wide-ranging military exercises is to Taiwan, the self-ruled island that Beijing claims as its own and has threatened to seize by force. Adm. Samuel J. Paparo, the head of the U.S. Indo-Pacific Command, describes Chinese military exercises around Taiwan as rehearsals for an invasion.

Along the Taiwan Strait, the roughly 100-mile-wide body of water that separates the island from mainland China, the threat is registered daily on the surface and in the air. Chinese military aircraft these days regularly cross a nominal median in the strait, Taiwan says, entering Taiwan’s de facto air-defense identification zone, or ADIZ, in numbers that would have been shocking only a few years ago.

President Trump has followed an American policy of not stating whether U.S. forces would come to Taiwan’s aid in the event of a Chinese invasion. A U.S. intervention is seen on the island as essential to preventing a takeover. For now, the U.S. sells weapons to Taiwan including missile defense systems, trains some of the island’s soldiers and aids its defense industry.

Defense Secretary Pete Hegseth told a gathering of defense officials in Singapore in late May that threats to Taiwan from China “could be imminent,” and warned of “devastating consequences” should Beijing seek to take over the island—part of a push for partners in the region to do more to counter China.

Senior Communist Party official Liu Jianchao told a July forum in Beijing that Hegseth’s remarks about China’s intentions were inciting “confrontation and conflict.”

Allied cooperation

The most visible example of the Trump administration’s push may be its pressure on Asian allies to spend 5% of their gross domestic product on defense.

That effort has encountered some resistance. Japan is seeking to raise its outlay to only about 2%, while South Korea said in June that its military spending was already “very high.”

The U.S. meanwhile maintains a security footprint in Asia that includes tens of thousands of troops on the Japanese island of Okinawa, less than 500 miles from Taiwan. About 55,000 U.S. military personnel are stationed in Japan and more than 28,000 in South Korea.

The U.S. military has beefed up its presence in the American territory of Guam, which already hosts several nuclear submarines and deployments of long-range bombers, by adding a new base expected to house 5,000 Marines.

The U.S. has no permanent troops based in the Philippines, but Manila has given U.S. forces access to more bases in recent years. The U.S. has stepped up its activities there, including by deploying the Army’s Typhon Missile System to the northern island of Luzon—putting Chinese military and commercial hubs within striking distance.

U.S. military exercises throughout the Indo-Pacific include extensive drills in far-flung islands, such as the recent delivery of a high-precision antiship missile system to a Philippine island 120 miles south of Taiwan. A three-week exercise involving 19 participating countries, Talisman Sabre 2025, began Sunday in Australia, with the U.S. coleading the event.

Beijing typically calls military exercises on its periphery provocative and destabilizing. In June, as a U.K. aircraft carrier group was making its way to Australia, a British naval vessel sailed through the Taiwan Strait for the first time in four years. Beijing denounced the passage and launched military drills that security officials in Taiwan described as a direct response.

“It’s clear that Beijing is really pushing back against the way democratic countries are coming together,” one of the officials said.

Write to Austin Ramzy at austin.ramzy@wsj.com and Emma Brown at Emma.Brown@wsj.com