To combat China, US wants its friends to do more

The path forward, articulated at a recent event in Hawaii attended by the U.S. and more than two dozen allies, was to sharpen their ability to jointly fight against Beijing by sharing intelligence, staging military exercises and ensuring their command systems can work together—in some areas for the first time.

The U.S. has struggled for years to beef up its military strategy in the Indo-Pacific, a region with a patchwork of alliances and partnerships with Washington. That’s a contrast with the unified structure in Europe with the North Atlantic Treaty Organization.

To illustrate the scale of Beijing’s ambitions and capabilities, Adm. Samuel J. Paparo, head of the U.S. Indo-Pacific Command, recalled how China in a single day last year deployed 152 warships, three-quarters of its amphibious forces and dozens of brigades to conduct aggressive maneuvers around Taiwan. Last month, China carried out large-scale drills there again.

“Rehearsals, not exercises," said Paparo, a four-star admiral who oversees U.S. forces in the region, in a keynote speech. “China is on a dangerous course."

Samuel J. Paparo, a four-star admiral who oversees U.S. forces in the Indo-Pacific region.

The military risk posed by China represents a key foreign-policy challenge for President Trump, who must get allies more aligned to combat Beijing while also negotiating trade deals over his “reciprocal" tariffs that have already caused friction with Asia-Pacific partners.

The Trump administration has identified China as the top national-security priority. On his first official visit to the region, Defense Secretary Pete Hegseth touted an “unprecedented" shift by the U.S. to the region.

Gen. Yasunori Morishita, who heads Japan’s army, said he has never seen a tenser security moment since he joined the country’s self-defense forces nearly four decades ago. He said the great risk posed by China meant Japan needed to be able to respond to any scenario.

Japan recently established a new joint operations command for its armed services, allowing for cross-branch coordination that previously would only have kicked in during a conflict or emergency. Tokyo also plans to deploy new homegrown counterstrike missiles by next March, Morishita said. Strengthening the alliance with the U.S. and other like-minded countries are two of Tokyo’s top priorities now.

“Building this network is so important," Morishita said.

The U.S. has recently added a second mobile “littoral regiment" team meant to hold key islands and deter China at the American military base in Okinawa, which sits just several hundred miles from Taiwan. That adds to the roughly 60,000 U.S. military personnel already stationed across Japan. During his Asia visit, Hegseth said the U.S. would also accelerate the establishment of a new joint U.S.-Japan military command in Tokyo, which he referred to as a “war-fighting headquarters."

China has unleashed an extraordinary military buildup in recent years, possessing a naval fleet now larger than the U.S., boosting incursions into neighboring airspace and ratcheting up maritime disputes across the region.

Taiwan, whose own defense strategy hinges on buying itself enough time for U.S. support to arrive, has contemplated a potential Chinese invasion as soon as 2027, with the Pentagon expressing a similar possible timeline.

China has pledged to seize control of Taiwan, potentially by force. To the U.S. and allies, a key goal for the initial phase of a potential showdown with China over Taiwan would be to neutralize China’s radar sites, missile launchers and command centers that hold off the U.S. and its allies, said Paparo, the Indo-Pacific commander.

China possesses several types of antiship missiles, a sizable lead in advanced hypersonic weaponry and an edge in its proximity to Taiwan. Paparo touted the addition of U.S. precision-strike missiles that can sink ships as a “gamechanger that fundamentally alters China’s risk calculus." New long-range hypersonic missiles add to the threat. So too do a pair of agile forces working closely with U.S. allies near Taiwan that can hit Chinese targets from land, collect valuable battlespace information and create openings for U.S. air and naval forces to maneuver.

The U.S. has roughly 380,000 military personnel across the Indo-Pacific region. But just a fraction of them are closest to the potential conflict areas around Taiwan and the South China Sea—a proximity struggle that military officials often refer to as the “tyranny of distance."

Many of the advances hinge on U.S. allies being willing to host American firepower on their own territory, expanding their own capabilities and knowing how to fight alongside one another. But big challenges remain to enable a cohesive response. For instance, certain allies and the U.S. are unable to share communications on a secured platform; they also have different military doctrines that dictate when and how a fight should be carried out.

Col. Charles W. Kean, who commands the U.S.’s 1st Multi-Domain Task Force, which works closely with the Philippines and other regional allies, said doors are opening with allies that previously were closed, owing to China’s rising aggression.

The U.S., which has kept an American missile system in the Philippines that has enraged China, has recently sent more military equipment to its treaty ally, including a lethal-strike missile. “So how do we complement each other with what uniqueness we’re able to bring to a situation or to solve a problem," Kean said.

America’s military also faces a shortage of available amphibious vehicles for transport, which would be key for any fight over Taiwan. That may require trade-offs, such as slower deployments of troops and supplies, said Lt. Gen. James F. Glynn, who commands Marine forces throughout the Pacific.

“It doesn’t mean we can’t respond," Glynn said. “It just means you have one less option."

In the Indo-Pacific, the U.S. has expanded bilateral—and increasingly multilateral—military exercises. It now conducts more than 40 annually, involving more than 20 allies.

Earlier this year, some 30 nations participated in the Cobra Gold drills in Thailand as participants or observers, with more than 8,000 military personnel involved. The exercises went beyond just the paratrooper tasks of the past, simulating electronic warfare and an amphibious landing.

“It’s really come a long way," said Lt. Gen. Matthew W. McFarlane, who commands America’s First Corps, which has more than 40,000 soldiers across the Indo-Pacific region. “But we’ve got work to do."

Write to Timothy W. Martin at Timothy.Martin@wsj.com