Only a few years ago, it would have seemed inconceivable that Japan would have any security role outside of Japanese territorial waters. But in a January 2015 interview, Admiral Robert Thomas, commander of the U.S. Seventh Fleet, related that Washington would welcome Japanese maritime air patrols in the South China Sea. He said that they could help to stabilize the region by balancing China’s growing naval strength there. That broke a long-standing taboo in Japan on public discussion of such uses for the Japanese armed forces. While it still may be some time before Japan mounts maritime air patrols over the South China Sea, yesterday it held an historic naval exercise in those waters.
It was the first time Japan’s Maritime Self-Defense Force ever conducted a bilateral exercise with the Philippines. Two Japanese destroyers and a Philippine corvette practiced how to deal with “unplanned encounters at sea.” They exercised near Subic Bay, a big Philippine (and former U.S.) naval base that is only 260 km from Scarborough Shoal—the spot where Chinese and Philippine patrol boats were locked in a months-long standoff in 2012 and where the Chinese coast guard used a water cannon to drive away Filipino fishermen just last month.
Even before the naval exercise, the Japanese and Philippine coast guards held a smaller drill in Manila Bay a week ago. Later this year, Japan will deliver the first of ten offshore patrol boats that it promised the Philippines in 2013. Manila plans to use them to better monitor its territorial waters in the South China Sea and prevent intrusions into them. Security ties between the two countries have grown substantially. Last year, Japanese Prime Minister Shinzō Abe invited Philippine President Benigno Aquino III to Tokyo to discuss greater security cooperation. At the time, Aquino went so far as to say that “nations of goodwill can only benefit if the Japanese government is empowered to assist others… especially in the area of collective self-defense,” giving a nod to Abe’s efforts to loosen Japan’s constitutional constraints that prevent his country from defending allies under attack.
Japan has also expanded its security activities with other Southeast Asian countries. Early this year, it mended ties with Thailand, whose coup led to a surge of Chinese influence there and strained relations with its longtime ally, the United States. In March, Japan signed an accord with Indonesia to enhance military exchanges and collaboration on defense equipment development. And Japan has steadily expanded its military cooperation with Vietnam, another claimant in the South China Sea dispute. Japan promised it offshore patrol boats too. In fact, immediately after the Japanese coast guard finished its drill in the Philippines last week, one of its cutters proceeded to Vietnam to participate in an exercise there. Japan has clearly sought a greater role in the security of the region.
Nonetheless, there is a question of whether Japan’s military can sustain a wider role. Contrary to China’s claims, Japan’s defense budget has not grown much. It rose less than three percent in the last year (and not at all in U.S. dollar terms). Any real expansion of Japanese military presence in Southeast Asia will have to run on a shoestring until Tokyo can afford a true increase in military spending. That is not to say Japan is without options. Its new long-range P-1 maritime patrol aircraft would be useful for patrols over the South China Sea. Moreover, Japan could enlarge its navy by simply slowing the pace at which it decommissions older warships, many of which are still highly capable. But there are limits too. Keeping older warships in service entails higher maintenance costs which may crowd out investment in new weapon systems.
As Japan expands its security role in Southeast Asia, new questions will arise. Foremost among them is whether Japan’s new role will lead to greater stability or instability? On the one hand, the absence of an adequately balancing force in Southeast Asia has given China a free hand to assert itself in the South China Sea, as marked by its massive land reclamation activities in the Spratly Islands. Given how grindingly slow America’s rebalance to Asia has been, Japan’s security support could be just what the region needs.
On the other hand, any minor incident between Chinese and Japanese forces in the South China Sea could easily escalate tensions between their two countries. Anyone who remembers the accidental collision between an American EP-3 surveillance plane and a Chinese J-8 fighter in 2001 can imagine how a similar incident between Japanese reconnaissance aircraft and intercepting Chinese fighters could spiral into a major crisis. Let us hope deterrence prevails.
 Mynardo Macaraig, “Philippines and Japan hold historic naval drills in flashpoint waters,” AFP News, May 12, 2015; Manuel Mogato, Adam Rose, and Ben Blanchard, “Philippines, Japan coast guards hold anti-piracy drills,” Reuters, May 6, 2015.
 Louis Bacani, “Aquino: Beneficial if Japan can defend allies under attack,” Philstar.com, Jun. 24, 2014, http://www.philstar.com/headlines/2014/06/24/1338501/aquino-beneficial-if-japan-can-defend-allies-under-attack.
 Rosemarie Francisco, Manuel Mogato, Linda Sieg, Tim Kelly, and Nobuhiro Kubo, “Japan steps up maritime engagement with Philippines, Vietnam,” Reuters, May 12, 2015; “Japan – Indonesia Joint Statement: Towards Further Strengthening of the Strategic Partnership Underpinned by Sea and Democracy,” Ministry of Foreign Affairs of Japan, Mar. 23, 2015; Mitsuru Obe, “Japan Reaffirms Economic Ties With Thailand,” Wall Street Journal, Feb. 9, 2015; Bagus BT Saragih, “Indonesia and Japan improve military ties,” Jakarta Post, Jan. 30 2013.