Japan's Air Self Defense Force (ASDF) is holding aerial refueling exercises with the U.S. Air Force from April 21 to May 2, the first such exercises for the ASDF — ever. The exercises, which are taking place over western Kyushu and Shikoku, involve Japanese F-15 fighters and U.S. KC-135 tankers. The training is part of Tokyo's preparation for the acquisition of its own in-air refuelers within the next few years. Japan long shied away from incorporating tanker aircraft into its own inventory or from training with U.S. carriers, since Article Nine of the Japanese Constitution states "land, sea and air forces, as well as other war potential, will never be maintained." But as Japan reinterprets Article Nine and moves toward a complete rewrite of its post-World War II constitution, the United States is encouraging the change as part of a broader strategic plan for East Asia. STRATFOR has monitored the evolution of Japan's defense policy over several years, noting the accelerated pace since Prime Minister Junichiro Koizumi rose to power. Japan's review of Article Nine, the so-called war-renouncing paragraph of the 1946 constitution, has been driven by the end of the Cold War, which left Tokyo's role in the U.S. defense system in question. Through the early 1990s, Tokyo and Washington's defense priorities slipped out of sync, leaving Japan seeking a more proactive domestic defense establishment. But as the international system started to equalize a few years after the collapse of the Soviet Union, Washington and Japan both saw the same long-term strategic threat: the rise of China. Washington since has tacitly and actively encouraged Japan to alter its defense policy and to do away with the constitutional limitations on its armed forces. The joint refueling exercises are only the most recent example of Tokyo-Washington cooperation in moving Japan further from its self-imposed military restrictions. Washington is interested in Japan moving beyond its current role as a base for U.S. forces into one of a true ally in the Asia-Pacific region. Japan has a high-tech defense force and could be a valuable assistant in monitoring and maintaining regional security. It also would be a very necessary partner in any confrontation with China. In fact, Washington already has floated the idea of building a Pacific defense triangle linking the United States, Japan and Australia — with Canberra primarily responsible for Southeast Asia, Tokyo focusing on Northeast Asia and Washington coming into the region in large force only when necessary. But the re-arming of Japan — or more directly, the lifting of restrictions on the operations and range of Japan's existing military forces — obviously would stir distrust in China and North Korea. It also would raise concern in South Korea, which eyes Japan with suspicion. Washington already views South Korea as a useful and necessary, but occasionally unreliable, ally. Seoul and Washington have different views on the best way to deal with North Korea and on the level of threat posed by China and Japan. Washington sees an eventually reunified Korea taking a more neutral stance, straddling the fence between two major powers. Just as Myanmar carefully balances relations with India and China, a unified Korea would not want to damage relations with either the United States, a key economic partner, or China, a neighboring country, but instead remain on the fringes of their competition. Given Seoul's likely move toward a more neutral role rather than a close defense ally of the United States, Washington is left with Tokyo as both the obvious and necessary partner in Northeast Asia. In the long run, Washington feels it is better to have an active military ally in Tokyo — despite the potential political fallout in the region — than to risk facing off with China with only minimal support or capabilities in Japan. And if the eventual clash with China never materializes, there is little lost from gaining another full regional security partner that could be called upon to deal with small-scale disturbances, freeing up U.S. forces for broader missions in other regions.