This opinion article first appeared in the Washington Post.

Most world leaders, including President Biden and Japanese Prime Minister Fumio Kishida, agree that the defense of Taiwan is crucial for regional security. But most options for improving deterrence will take too long. Building Taiwan’s self-defense, developing more U.S. firepower in the region, creating the economic resilience to make severe sanctions feasible: None of these will come to fruition before 2030.

Japan could change the game now. Allied forces, responding immediately and en masse, have a chance of thwarting a Chinese invasion, according to a recent report from the Center for Strategic & International Studies. But, in meetings with high-level officials in Tokyo last month, I sensed a mismatch between talk and walk. Japan must broaden its vision of self-defense to encompass priorities and declaratory policies that will avert calamity in the region. Tokyo cannot wait until war breaks out to start the tougher conversations.

Here’s why.

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First, without Japan, the United States could be outgunned in a fight to defend Taiwan, notwithstanding Washington’s new basing agreement with the Philippines. A combined U.S.-Japan fleet, on the other hand, would boast more than three times as many aircraft carriers, cruisers and destroyers as the People’s Liberation Army Navy. The quality of many Japanese ships approaches that of its U.S. counterparts. Eight of Japan’s destroyers field a state-of-the-art Aegis weapons system used by some of the more advanced ships in the U.S. Navy.

Second, Japan’s involvement could mitigate some of the geographic vulnerabilities of the United States. Adding Japanese bases more than doubles the locations from which the two countries together could conduct operations. Japan’s southwestern islands are closer to Taiwan than mainland China. Take Yonaguni Island, just about 70 miles from Taiwan’s east coast. On it are intelligence, surveillance and reconnaissance assets, as well as anti-ship and anti-aircraft capabilities. Operating from these bases in the defense of Taiwan, allied forces would have more opportunities to quickly target an invading force. That would make attacks on U.S. bases in Japan, such as Kadena, at the southernmost tip of the archipelago, less attractive to the Chinese. Such strikes would no longer completely cripple an air effort.

Third, Japan has military strengths that would make a fait accompli almost impossible for China. Though Japanese diesel submarines are slower than U.S. counterparts, they could reach the Taiwan Strait in just two days. U.S. submarines departing from Hawaii would take at least a week; from San Diego even longer. This makes Japan the first line of defense for Taiwan. Japanese boats could also monitor key choke points through which Chinese navy submarines would be attempting to exit the First Island Chain in the western Pacific. This would free up the quieter submarines of the U.S. Navy to wreak havoc on amphibious vessels and escort ships.

In short, Tokyo could contribute significantly to a military effort to deny China the ability to take Taiwan by force. To do so, Japan must increase its stockpile of torpedoes and long-range strike weapons, as planned. Tokyo must be willing to go after the amphibious invasion force and targets on mainland China — a very controversial proposition indeed.

On the surface, it looks as if Japan is moving in the right direction. The government took the groundbreaking historic step of increasing defense spending to 2 percent of Japan’s gross domestic product over the next five years. This meant a whopping 26.3 percent increase in 2023 alone. The greatest increase in the past was in 1986, by nearly 50 percent.

Last year, former prime minister Shinzo Abe stated that the security of Japan is connected to Taiwan. He said a Chinese use of force against a U.S. vessel defending Taiwan could legally trigger the deployment of Japan’s military (known as the Self-Defense Force).

Indeed, a 2015 law allows Japan to engage in collective defense when presented with an existential threat. This provides plenty of flexibility for Japan to fight alongside the United States without the need for a constitutional amendment. The officials I spoke with in Tokyo were firm that Japan would respond if China attacked U.S. bases such as Kadena.

But all these initiatives concern self-defense. Japan does worry that military activity around Taiwan could extend to the security of its southwestern islands. Or that if China takes Taiwan, it would be emboldened to take the Senkaku/Diaoyu islands, which Tokyo administers but which China also claims. There are even concerns that Okinawa, a group of 160-plus islands that is home to 1.4 million people (and dozens of U.S. bases), could then prove enticing to Beijing.

Crudely, Japan seems to be prepared to push back against only Chinese assets that are clearly poised to attack its sovereign territory. Those heading toward Taiwan? Not so much.

While a degree of strategic ambiguity makes sense, too much could backfire. If Japan is clearly unwilling to defend Taiwan, then improvements in Japanese military capabilities will do little to deter conflict across the strait. Japanese officials don’t need to say they would attack any Chinese invading forces, but they need to let their counterparts know it is a real possibility. The officials I met were unwilling to send such strong messages; some insisted reassuring Beijing was more important.

Tokyo must make clear at home and abroad that defending Taiwan is no longer off the table. The prospect of Japan engaging in offensive operations in the defense of Taiwan would stay Chinese President Xi Jinping’s hand. Only then would recent monumental changes in Japanese politics fulfill their potential in contributing to peace and security in Asia. If Ukraine has taught us anything, it is that deterrence is costly, but war is worse.