Japan’s first-ever national security strategy, released this week, may prove to be an inflection point in twenty-first-century Asia’s young history. Not only had Japan abided by a strict interpretation of its U.S.-written pacifist constitution over the last six decades, but Japan’s people had adopted pacifism as an important part of their national identity. And yet, somewhat suddenly, a country that has been not just wary of but eager to avoid foreign military entanglements is now implementing a more “proactive” national security policy. Its plans are good for Japan, good for Asia, and good for U.S. interests.

While Prime Minister Shinzo Abe is owed Washington’s thanks for his steely leadership, congrats are also in order for Beijing. China has done what North Korean belligerence and American goading have long failed to do: awake Japan from its Rip Van Winkle-like postmodern slumber. Just four years ago, Japan’s then prime minister Yukio Hatoyama was seeking to distance Tokyo from Washington and pushing the formation of an Asians-only “East Asian Community.”

But now, according to the National Security Strategy, Japan lives in a “severe security environment.” Leaving little doubt as to the responsible party, the strategy document accuses China of “attempts to change the status quo by coercion,” intruding “into Japan’s territorial waters and airspace around the Senkaku islands,” and “unduly [infringing] the freedom of overflight above the high seas.”

Recent years have seen the Chinese navy regularly transit through the Japanese islands to the Pacific Ocean. In the fiscal year ending March 2013, Japan scrambled fighter jets 306 times in response to Chinese aircraft, a record high and the first time Chinese-induced scrambles outpaced Russian-induced ones.

Chinese and Japanese maritime forces, moreover, have been playing an ongoing game of cat-and-mouse in the East China Sea, the result of a Chinese effort to change the reality of Japan’s administrative control over the disputed Senkaku islands. Most recently, Beijing declared an “air defense identification zone” over much of the East China Sea, including the Senkakus, claiming that civilian and military aircraft within the ADIZ are required to file flight plans with China and are subject to Chinese directions. While many point to the Japanese government’s purchase of three of the islands last year as the starting point for the latest round of tension, Chinese pressure on the islands had been a near constant before then.

Beijing’s approach to the Senkakus is often attributed to Chinese nationalism and a new president, Xi Jinping, more inclined to act on nationalistic sentiment than his predecessor. But there is more to it than that. Indeed, Chinese actions in the East China Sea, including regular Chinese submarine passage through the Miyako Strait, highlight what Beijing sees as a key vulnerability—its lack of control over the waterways through which its exports, natural resource imports, and naval vessels must pass.

China has become one of the world’s most dependent nations on international trade, most of which is carried by merchant vessels. Those ships dock at the massive ports along the only Chinese shoreline, in places such as Shanghai and Ningbo. China has, as a result, been building the naval power to protect its maritime trade. China is now a land power trying to go to sea. But to become a true maritime power it must pass through the East and South China Seas to reach the Pacific and Indian oceans.

From China’s perspective, the “first island chain”—which stretches from the Japanese home islands in the northeast through the Ryukyu islands and Taiwan to the Philippines in the Southeast—remains a potential obstacle to Chinese access to the Pacific and a platform from which potential adversaries can interdict Chinese maritime traffic, whether of the military or commercial variety.

With its stepped up naval transits through the Ryukyus and its unrelenting approach to the Senkakus, Beijing has telegraphed to Tokyo and Washington what it is most concerned about. To its credit, Japan is paving the way for a new U.S. maritime strategy that can take advantage of Chinese vulnerabilities.

While the new national security strategy discusses North Korea, terrorism, the Middle East and the global commons, Japan’s defense reforms are focused largely on securing the Ryukyu island chain, and the Senkakus in particular, thus continuing the country’s rebalance of security emphasis and resources from Russia in the north to China in the west (now, that’s a real rebalance).

And although Tokyo is driven by concerns for the security of its own territory, it is also taking advantage of the geographical edge it hold vis-à-vis China. Japan is already an impressive naval power with a very strong submarine and destroyer fleet. In accordance with its new plans, it will add a number of important new capabilities, including first-class maritime air interdiction, stealthy strike, rapid reaction forces, and C4ISR. All of these capabilities will be useful in defending Japan’s southwestern islands, but just as important, they will also allow the Self-Defense Force to operate more effectively in an international coalition.

Washington can multiply the effect of Tokyo’s new defense policy with a real defense strategy of its own. U.S. forces can build facilities, field new capabilities, and help upgrade allied forces in a region stretching from Indonesia through the Philippines and Taiwan and up to Japan that can together bottle up the Chinese navy. Doing so would force Beijing to spend heavily on defenses, such as antisubmarine-warfare capabilities of its own. The U.S. can also lead an effort to build a coalition maritime domain awareness center that each country in the first island chain can plug into. Taken together, these steps could complement the robust presence of American and allied undersea, mining, and surface-warfare forces, all in the service of causing China to think twice about sticking to its current coercive strategy.

Japan has started the process of regaining the initiative from China. Washington now has a chance to lead its allies in a strategy that forces China to play defense. Will it?

Dan Blumenthal is a resident fellow at the American Enterprise Institute. Follow him on Twitter: @DAlexBlumenthal. Michael Mazza is a research fellow in foreign and defense policy studies at the American Enterprise Institute. Follow him on Twitter:@Mike_Mazza