This report looks at the pros and cons of the alliance with Japan, in which the United States maintains exclusive use of 89 military bases in Japan and, in exchange, guarantees Japan's security. The alliance has endured over 50 years, through periods of intense partnership and stretches of political drift; this report reevaluates the relationship based on international developments.

The huge earthquake and tsunami that struck Japan's Fukushima Daiichi nuclear power station on March 11, 2011, knocked out backup power systems that were needed to cool the reactors at the plant, causing three of them to undergo fuel melting, hydrogen explosions, and radioactive releases. Radioactive contamination from the Fukushima plant forced the evacuation of communities up to 25 miles away and affected up to 100,000 residents, although it did not cause any immediate deaths. Studies of the Fukushima disaster have identified design changes, response actions, and other safety improvements that could have reduced or eliminated the amount of radioactivity released from the plant. As a result, Fukushima has prompted a reexamination of nuclear plant safety requirements around the world, including in the United States.