The revised bilateral agreement on logistical cooperation between military forces of Japan and the United States, for which the government plans to seek Diet approval during the ongoing session, significantly expands the scope of the Self-Defense Forces' support of the U.S. military not just in geographical terms but in the nature of the support they provide. The accord is yet another step for full implementation of the Abe administration's security legislation that came into force in March, but the changes in SDF missions in support of U.S. forces was not discussed in full detail when the legislation — a package of a new law and amendments to 10 existing laws — was deliberated in the Diet last year. Lawmakers should spend enough time to highlight what the revised bilateral accord will entail for Japan's overseas military missions.

Since it was first concluded in 1996, the Acquisition and Cross-Servicing Agreement (ACSA) has been updated in line with the expansion in bilateral defense cooperation. Initially, the mutual provision of supplies such as food, water and fuel as well as transportation, lodging and other services between the SDF and U.S. forces was limited to peacetime cooperation such as joint exercises and United Nations-led peacekeeping operations. The scope of logistical cooperation was expanded to contingencies in areas surrounding Japan in 1998. The agreement was revised again in 2004 to enable supply of ammunition to U.S. forces in "noncombat" areas when enemy attack on Japan was either taking place or anticipated.

The revised agreement signed by Tokyo and Washington in late September brings SDF troops providing logistical support for U.S. forces much closer to the battlefield. The previous government policy dictated that Japanese troops in such missions operate only in "noncombat" zones — explained as areas where the fighting is currently not taking place and where fighting is not expected to occur over the duration of the support mission — so that the SDF troops providing the logistical support would not become an integral part of the use of force by the other forces in combat missions, as prohibited by the war-renouncing Article 9 of the Constitution.