Japan's policymaking strategy in foreign and defense affairs changed dramatically in 2001 after Prime Minister Junichiro Koizumi took the helm of the long-ruling Liberal Democratic Party. Following a series of bland and short-lived prime ministers, Koizumi's infusion of fresh energy into a tired and opaque party has been compared with Tony Blair's successful revamping of New Labour in the U.K. Koizumi, however, had a weak power base in the party and limited diplomatic experience. How, then, was he able to exercise leadership?

Tomohito Shinoda analyzes the prime minister's role in...

Shinoda provides an analytical framework for examining the role of the prime minister in Japan's political decision making. He shows that two dimensions of fraction within the government and the ruling party--interagency rivalry and intraparty factions--confront the prime minister whenever a major policy issue needs to be resolved. Despite these obstacles, Shinoda shows that the prime minister can be effective.

First, Shinoda identifies the sources of power available to Japanese prime ministers--some from legal authorities and others from informal sources. Because prime ministers must...