During the past fifteen hundred years, the Korean peninsula has frequently been at the forefront of Japanese debates about Japan’s place in its region. In particular, two turning points decided Japan’s involvement in East Asia prior to 1945. The first occurred in 663, after the Japanese defeat in southwestern Korea (then called Paekche) forced them to retreat from the continental bridgehead that had been established. With the exception of the invasion of Korea by Hideyoshi at the end of the sixteenth century, this retreat from active involvement on the Asian mainland endured for twelve hundred years, ensuring a level of Japanese autonomy from continental Asia far beyond that of (for example) England from continental Europe.