This book demonstrates how the Yoshida Doctrine, named after the Japanese Prime Minister who in 1951 negotiated with the United States the end of the post-war Occupation, has continued since 1951, and continues still, in modified form, to be the foundation of Japan "s security policy. It shows how the aim of Yoshida was to ensure Japan "s security at minimum cost, so that resources and the energy of the Japanese people could be concentrated on economic reconstruction and development, and how this was achieved by the asymmetric alliance with the United States, which shifted the burden of defending Japan to the United States, and by the "peace clause" “ Article 9 “ of the Japanese constitution, which prohibits the possession of armed forces. The book argues that the Yoshida Doctrine has been remarkably successful in achieving what it set out to achieve, and remarkably flexible, being adapted following the end of the Cold War to fit new circumstances. It discusses how the Yoshida Doctrine and Japan "s security policy have been formed as much by domestic issues and debates within Japan as by external threats and the need to counter them, and it assesses how the Yoshida Doctrine has led to Japan being a very passive player in international relations, reluctant to take on the more proactive role demanded of Japan by the United States in recent decades, and increasingly dependent on the United States, despite Japan "s potential for self-assertion.