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Japan and the United States on Tuesday marked the 50th anniversary of the signing of the current Japan-U.S. security treaty. Under the treaty the U.S. and Japan are to act jointly in defending against an attack on Japanese territory or on U.S. bases in Japan.

The signing of the treaty in 1960 met strong opposition from those who feared it would increase the possibility of Japan's involvement in war. Despite initial opposition and changes in the international environment since then, notably including the end of the Cold War, the security treaty has survived. In 1996, Japan and the U.S. declared that the role of the security setup had expanded to securing peace and stability in the Asia-Pacific region.

In separate statements, U.S....