"The U.S.-Japan alliance, forged in the U.S. occupation of Japan after its defeat in World War II, provides a platform for U.S. military readiness in Asia. Under the Treaty of Mutual Cooperation and Security, about 53,000 U.S. troops are stationed in Japan, providing the major U.S. forward logistics base in the Asia-Pacific. The United States has the exclusive use of 85 facilities throughout the archipelago; Okinawa hosts 37 of the facilities. The U.S.-Japan alliance was originally constructed as a fundamentally asymmetric arrangement--Japan hosts U.S. military bases in exchange for a one-sided security guarantee--but this partnership has shifted toward more equality. Japan boasts its own sophisticated defense assets and the two militaries have improved their bilateral capabilities as a combined force. The phrase 'U.S.-Japan alliance' can describe a wide range of cooperative activities and programs, but this report focuses on the political and military partnership between the United States and Japan."
CRS Report for Congress, RL33740
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html