TRIBUTES TO mark the sixtieth anniversary of the U.S.-Japan Security Treaty last January celebrated the vision of its creators and its modern indispensability. Certainly, the successes are real. The treaty has kept a former enemy and advanced industrial power aligned with the United States and served as the foundation of America’s geopolitical position in East Asia. Japan is America’s most important ally in the region. But it is also worth remembering that the U.S.-Japan relationship owes a large measure of its success to good fortune. Over sixty years it has never been tested in a great power crisis. And fortune has bred complacency, especially on the American side.

The policy case for the U.S.-Japan alliance is little changed since the end of the Cold War. That view is of a “bases for protection” bargain in which Japanese military restraint and U.S. primacy keep the Asian peace, leavened by occasional American requests that its passive client support U.S. global strategy and improve interoperability with the U.S. military. The growth of Chinese power, the relative decline of America’s, and Japan’s response have undermined key aspects of this story.

Today, Japanese military power is sufficient to heighten Chinese insecurities but insufficient to help slow or arrest East Asia’s deteriorating military balance. The American bases at the core of the alliance bargain are vulnerable to new generations of Chinese precision weapons and a source of crisis instability. And Japan is no longer a reactive state. Alarm at Chinese power, concern about U.S. abandonment, and institutional reforms give the prime minister’s office the motivation and capacity to sustain a degree of foreign policy autonomy unthinkable in 1990. The United States risks overindulging Japanese policymakers’ appetite for security reassurance vis-à-vis China, to the detriment of regional stability. 

The United States has two basic interests in East Asia: keeping the region free from hegemonic domination and preserving peace and stability among the major powers. The alliance with Japan has been our core tool for serving these purposes, but regional security developments should cast doubt on its ability to continue to do so in its current form. Asia’s security environment is more fragile than at any time since the Korean War, and America’s geopolitical margin for error is shrinking. Our most important alliance needs a critical look before its sixty-year run of good fortune comes to an end.

A CENTRAL rationale for U.S. alliances claims that they inhibit regional security competition by making it unnecessary for allies to build big militaries that could threaten their neighbors. This argument is particularly prominent in discussions of the U.S.-Japan alliance, which has been variously described as the “cork in the bottle” of resurgent Japanese militarism, the “cornerstone” of regional stability, and as an American “sword” paired with a Japanese “shield.” Henry Kissinger deployed it on his famous 1971 visit to China, assuring Premier Zhou Enlai that the alliance served Chinese interests by containing Japan. The cork metaphor is now passé, but it remains routine for alliance analysts to celebrate the stabilizing effects of Japan’s decision to forgo a military posture proportional to its economic power.

Yet the evidence suggests that Japanese military restraint is overrated. Decades of low Japanese defense spending have not dissuaded China from embarking on a huge military buildup or forestalled a worsening regional security dilemma. The dominant view in Chinese policy circles is that the U.S.-Japan alliance is an increasingly offensive arrangement meant to contain China’s rise and restore Japanese military power. This is aggravated by persistent Sino-Japanese tensions over Japan’s twentieth-century aggression against China and the gradual expansion of the alliance ambit to cover Taiwan, a core sovereignty and legitimacy issue for Beijing. Western analyses commonly observe that China’s military modernization began in earnest after the 1996 Taiwan Strait Crisis. Neglected are further likely motivators: the 1997 expansion of the U.S.-Japan alliance guidelines to include “situations in areas surrounding Japan,” obscure phraseology widely interpreted to include Taiwan, and the 2005 inclusion of Taiwan in a U.S.-Japan joint statement as a “common strategic objective.”

Nor are the Chinese wrong to believe that the alliance has taken on offensive characteristics. Post-Cold War developments in Japan’s military posture have deviated from a reasonable standard of qualitative restraint. Japan has fielded an array of advanced systems—often with American encouragement and cooperation—including guided-missile destroyers, pocket aircraft carriers, and a fleet of fourth- and fifth-generation fighters, all while sticking to its informal one-percent-of-GDP defense budget cap. Richard Samuels and Eric Heginbotham observe that “[t]he overwhelming bulk of Japan’s defense budget remains committed to capabilities consistent with a forward defense strategy.” These are maneuver forces with inherently offensive characteristics. So too with ballistic missile defense, the flagship project of U.S.-Japan defense cooperation. According to arms control expert Theodore Postol, the missile defense features of the Aegis missile system are mechanically indistinguishable from its offensive cruise missile-launching capabilities. It is telling that the Japanese government’s decision last June to cancel the acquisition of land-based Aegis systems quickly led to a national debate over whether to acquire long-range strike missiles instead.

The motivations behind China’s defense buildup are undoubtedly diverse, but it is hard to believe that having the combined potential of two of the world’s largest economies on its doorstep did not factor into its calculations. Japan has the right to defend itself from increasingly severe regional threats, but if the United States is sincere about preserving regional stability it must take Chinese perceptions seriously. Pretending that the alliance has not made its own contributions to the worsening regional security dilemma is a recipe for trouble.

Ironically, the extent of this worsening makes it imperative that Japan now abandon its commitment to quantitative restraint: the one-percent-of-GDP defense budget cap. Twenty-five years of Chinese military investment now significantly overshadow Japan’s capabilities. Where China’s defense budget roughly equaled Japan’s in the year 2000, it now spends five times as much in price-adjusted dollars, according to the Stockholm International Peace Research Institute. The most important result of this effort is a resilient, diversified stockpile of guided and ballistic missiles, a thousand of which can target allied surface ships and bases in Japan and several hundred as far as Guam. China now fields over eight hundred modern fighter aircraft against Japan’s three hundred, and the displaced tonnage of the Chinese navy is now almost double Japan’s Maritime Self-Defense Force. This fleet now includes cruisers which probably match the capabilities of Japan’s best Aegis ships. Forward-deployed U.S. forces alleviate but do not remedy Japan’s deteriorating position.

The U.S.-Japan alliance cannot “offset” China’s resources and proximity through budgetary brute force, and should not try. America’s basic regional security interests in hegemony prevention and military stability are inherently defensive and best secured by a denial strategy designed to convince China’s leaders that they cannot achieve a quick and easy victory. Such an approach would aim to avoid difficult, escalatory fleet-on-fleet battles near China’s frontier, where its natural advantages are the greatest. Instead, U.S. and allied forces would adopt a dispersed posture to reduce their vulnerability to a first strike, and field more missiles and submarines to jeopardize China’s own offensive potential. It would reassure Japan that its security does not depend on America’s declining capacity to win decisive battles in the First Island Chain. It would help convince China that U.S. goals are not offensive.

Though cheaper than a direct attempt to overcome China’s missile and proximity advantage, denial will require some Japanese heavy lifting. The U.S. government often claims to want a more equal alliance but is only ever willing to discuss burden-sharing in terms of host nation support payments and marginal tweaks to Japan’s junior role in a U.S.-led division of labor. It has never really sought a quantitative step change in Japan’s role. The likely growth path of Chinese military power makes this untenable. The United States needs Japan to accept serious resource tradeoffs, even if the result is a more militarily autonomous Japan. Last October, then-Secretary of Defense Mark Esper announced the United States expects every ally to adopt NATO’s two-percent-of-GDP defense spending target. That would be a good start, but there must also be pressure to meet it. In Japan’s case, the United States should make clear that it regards progress toward that goal as vital to a smooth alliance relationship. 

CHINA’S MILITARY challenge is also an unprecedented threat to U.S. bases in Japan, cutting at the central bargain of the 1960 Security Treaty. That document’s Article V security guarantee is followed by Article VI, granting America “the use by its land, air and naval forces of facilities and areas in Japan.” There are now fifty-four thousand American soldiers stationed at eighty-five sole-use U.S. bases across Japan, including roughly twenty-five thousand at thirty-three bases on Okinawa island in the southwest. Accounting for a quarter of peacetime U.S. overseas deployments, this force is the foundation of U.S. military power in Asia and the most visible symbol of America’s commitment to Japan’s security.

The facilities they occupy have long been a source of local political discontent, especially on Okinawa. Now they are also vulnerable to China’s missile force and a potential source of crisis instability. The most important—the air bases at Misawa, Yokota, and Kadena; the naval bases at Yokosuka and Sasebo; and the Marine Corps bases at Iwakuni and Futenma—were acquired and built into big main operating bases in an era of uncontested U.S. air and sea dominance. Today, their heavy concentrations of forces would be appealing targets for preemption in a Sino-American crisis. The RAND Corporation estimates that thirty-six ballistic missiles could disable the runways of the Kadena Air Base in Okinawa, the largest in the region, for four days. Planes stranded on the ground would be easy prey. The U.S. military is beginning to address this vulnerability with doctrinal changes emphasizing resilient, mobile platforms and dispersal of forces across greater numbers of small bases.