While Japan had long kept an isolationist policy, it had periods where that wasn't quite true. Imperial Regent Hideyoshi Toyotomi decided to conquer Korea and China. In 1592 Japan had invaded Korea and occupied a good chunk of its lands. Korea was allied with China and with help from the Ming dynasty they were able to deter Japanese forces from taking either country. Hideyoshi Toyotomi died in 1598 and his conquest withered away shortly afterwards.