The US-Japan alliance is confronting its most critical test since its inception in 1951. It is facing a new evolutionary stage in a radically-changed context, with the rise of China, Asia's economic crisis, and Japan's economic deadline and political immobility. This is an overview of the process of "redefining" the US-Japan alliance. It presents four specific case studies: the impact of macroeconomic and trade frictions on the alliance; the effect on the functions of the alliance of the suspicions about North Korea's nuclear programme; the vehement protests against the alliance triggered by the rape of an Okinawan schoolgirl by US servicemen in 1995; and the challenges to the alliance posed by the straining of sino-American relations over Taiwan and the Chinese missile tests in 1996, which prompted America's decision to dispatch an aircraft carrier to the region. These events were all part of the "redefining" process, a process which continues.