As a supporter of Yoshida Shigeru, he advocated cooperation with the USA in the immediate post-war period. Forced from the cabinet over allegations of corruption in 1954, he returned four years later and between 1964 and 1972 served as Prime Minister. He overcame a period of student violence, oversaw the extension of the revised United States Security Treaty (1970), negotiated with the USA for the return of Okinawa and the other Ryukyu islands, and normalized relations with South Korea. After leaving office he received a Nobel Peace Prize for his efforts to make Japan a nuclear-free zone.