Would Allies Fight With U.S. for Taiwan? Japan Is Wary

TOKYO—American and Japanese military officials have been working on a plan for a conflict over Taiwan for more than a year, but the talks have yet to resolve a central question: Would Japan join the fight?

Washington has nudged Tokyo to consider roles for the Japanese military such as hunting for Chinese submarines around Taiwan, said people familiar with the discussions, without getting any commitment.

The planning is one of the most important aspects of the U.S. response to Beijing’s threats to capture Taiwan by force. At its closest, Japan is just 70 miles from the democratically self-governing island, and it hosts some 54,000 U.S. troops, concentrated on the southern island of Okinawa.

If China moves to seize Taiwan and the U.S. intervenes, as President Biden has said it would, the first response would likely come from those U.S. bases. Under an agreement dating from the 1960s, the U.S. would need Japan’s approval—but Tokyo would feel pressure to provide that, as refusing would jeopardize the alliance that ensures its security.

Getting Japan to engage in the fight directly would be harder. Japanese leaders publicly shun discussion of a role in any Taiwan war, in part because public opinion is generally against getting ensnared in a conflict.

“If you ask the question of whether you are willing to risk your life to defend Taiwan, I think 90% of Japanese people would say ‘no’ at this point,” said Satoru Mori, a professor of politics at Keio University in Tokyo.

Tokyo is investing heavily in long-range cruise missiles and other hardware in response to China’s growing arsenal, but it says the buildup is strictly for self-defense. “We have to spend more on military deterrence and response capabilities to reduce the risk we would be attacked,” Prime Minister Fumio Kishida said on a recent visit to Okinawa.

Japan’s Constitution, written by the U.S. after World War II, renounces the use of force to settle disputes. But under a law approved in 2015 under then-Prime Minister Shinzo Abe, Japan can respond militarily if a close ally is under attack nearby and its own survival is at stake.

Simulations conducted earlier this year by the Center for Strategic and International Studies, a Washington think tank, found the U.S. could likely block a Chinese takeover of Taiwan with the support of allies such as Japan and Australia.

In most of the center’s wargame scenarios, Japan joins the U.S. in the fight after China attacks U.S. bases on Japanese soil, destroying hundreds of American and Japanese aircraft—a modern-day version of Pearl Harbor. Surviving Japanese ships and planes attack the Chinese to the north and east of Taiwan and help intercept Chinese amphibious invasion craft before they overwhelm the island, with Japan’s hard-to-detect submarines playing a vital role in sinking Chinese ships.

While a Chinese attack on U.S. bases in Japan would likely end Tokyo’s hesitancy, some American and Japanese security analysts said, there is no guarantee a conflict would play out that way. What worries Tokyo most about getting involved in fighting is the risk of escalation—for example, of China’s encouraging allies Russia and North Korea to attack Japan, or threatening to use nuclear weapons.

The U.S. is seeking more clarity from Japan as the two sides try to develop a combined operational plan for a Taiwan conflict. Subjects include supply routes, missile-launcher sites and refugee-evacuation plans, people familiar with the talks say. Japan is willing to support the U.S. military by providing fuel and other supplies, these people say.

A Pentagon spokesman said the U.S. and Japan share a commitment to peace in the Taiwan Strait and that the U.S. welcomes Japan’s interest in “expanding its roles, missions, and capabilities. This will enhance deterrence.” Asked about planning for a conflict over Taiwan, a Japanese government spokesman said Japan and the U.S. maintain joint defense plans but declined to go into further detail.

Japan’s military, known as the Self-Defense Forces, currently operates 50 destroyers and 22 attack submarines, as well as more than 300 jet fighters. Late last year, Tokyo said it would raise military spending around 60% over the next five years to 2% of gross domestic product.

Japan plans to have Tomahawk missiles obtained from the U.S. and its own long-range cruise missiles ready for use some time after spring 2026. Its fleet of F-35 stealth fighters is set to grow from around 30 to 147, the largest contingent outside the U.S.

“We are building up our army, navy and air force, as well as space and cyber capabilities. Maybe in five years when our new shape is clearer, we will have to talk about new roles and missions in the region,” said Nobukatsu Kanehara, a former national-security official and adviser to Abe, the former prime minister.

In a 2021 fundraising speech, then-Deputy Prime Minister Taro Aso said that a war over Taiwan could risk Japan’s survival, which would justify Japan’s helping defend the island.

But Keio University’s Mori said the lack of meaningful public discussion in Japan about why Tokyo should support Taiwan’s defense could lead to political chaos if the worst comes to pass. Without a clear position, the government would struggle to manage the U.S. alliance while dealing with public concern, he said.

Kishida is sensitive about suggestions he is just following Washington’s direction. In a speech last month, Biden took credit for Japan’s military buildup, saying of Kishida, “I convinced him.” Kishida’s government said it complained to Washington, and Biden later said the prime minister had already decided to raise military spending.

At a North Atlantic Treaty Organization summit this week, Biden praised Kishida for increasing Japan’s defense budget and supporting Ukraine.

Tight civilian controls on Japan’s military, imposed after World War II to prevent a return to the country’s militaristic past, could slow decision-making at a time when a few lost days could determine Taiwan’s fate, experts warn.

“Most likely when we can fight together, we will,” said Rui Matsukawa, a former Japanese vice defense minister. But Japan wouldn’t look to be on the front lines, she added.

—Chieko Tsuneoka contributed to this article.

Write to Alastair Gale at [email protected]