Despite its extensive, multilayered economic relationship with China, the United States has moved gradually but inexorably over the past decade or so to put in place the building blocks of a policy to contain Chinese power. Washington has forged new security relationships with nations that were once regarded as less than friendly. India is the prime example. U.S. officials are not even especially subtle in their courtship of Delhi as a possible ally against Beijing. Indeed, India has been the more reluctant, cautious party in that evolving relationship. Washington has even developed strategic ties with onetime outright enemy Vietnam. This summer, the Obama administration lifted the long-standing arms embargo against that country, and the U.S. Navy can barely restrain its interest in gaining access to the deep water port at Cam Ranh Bay.

The containment strategy has also included attempts to revitalize, strengthen, and broaden Washington’s relations with traditional East Asian allies. Sometimes, the effort has failed. The most graphic case, after a promising start, involves the going divorce taking place with the volatile regime of Rodrigo Duterte in the Philippines. But at other times, that strategy has worked, notably with South Korea and spectacularly so with Japan. Indeed, Tokyo not only seems eager to participate in Washington’s balancing strategy against Beijing, it has taken a surprising number of initiatives of its own.

As early as 2013 and 2014, Tokyo was clearly backing the Association of Southeast Asian Nations (ASEAN) in its South China Sea territorial disputes with China. Japan’s involvement in the South China Sea has since escalated on multiple fronts. Japanese ships will now join U.S. naval vessels in conducting so-called freedom of navigation patrols in that body of water&mdsah;a move that has caused Beijing to issue a sharp denunciation. Indeed, China objects even to Japanese diplomatic involvement in the South China Sea territorial disputes.

In addition to its own military involvement in the South China Sea, Tokyo has agreed to provide patrol ships to Vietnam, one of Beijing’s most intense rival claimants. In late September, Tokyo agreed to do the same for Malaysia, another rival claimant. Japan also offered maritime support, including used military hardware, to the Philippines (although that was before Duterte’s rapprochement with Beijing), and Tokyo has developed a variety of security ties with Indonesia. When it comes to the South China Sea, Japan’s attitude appears to be “anybody but China.”

Perhaps most disturbing to Beijing, Tokyo’s ambitions do not seem confined to the South China Sea. Prime Minister Shinzo Abe’s government continues to negotiate a $1.65 billion deal to sell amphibious military aircraft to India and seeks closer maritime security ties. Indo-Japanese security cooperation has developed to the point that Columbia University Professor Rajan Menon, a respected expert on international affairs, wondered whether a de facto alliance between Tokyo and Delhi might be forming. Although the notion of an Indo-Japanese strategic alliance is both premature and excessive, Tokyo certainly seeks to keep its options open.

It should not be surprising that Japan has apparently embarked on a balancing strategy toward China. Beijing’s own conduct, including pressing its territorial dispute with Tokyo over the Diaoyu/​Senkaku islands in the East China Sea, has made Japanese policymakers increasingly nervous. So does China’s growing military capabilities. The last two Japanese defense white papers single out China as the nation’s principal security threat.

The alternative to joining a U.S.-led balancing or containment strategy would be to bandwagon with China as a junior partner in a new East Asian bloc. There appears to be little or no appetite for such a humbling option among members of Japan’s political and economic elite. That is especially true with Abe’s right of center government.

One intriguing question is how much of the balancing behavior that Tokyo is exhibiting is a response to encouragement or pressure from the United States and how much is the result of independent initiatives on the part of the Japanese. Chinese leaders would probably like an answer to that question as well. Do they face a united (and more robust) U.S.-Japanese diplomatic and military front—but one under secure U.S. control? Or do they now face a Japan that has embarked on its own ambitious containment policy, reflecting a nationalist agenda that may not be entirely amenable to American restraints? The evidence is unclear at this point, but the situation bears watching.