On August 9, 1974, he resigned in the face of almost certain impeachment and removal from office—the only time an American president has done so. After his resignation, he was issued a controversial pardon by his successor, Gerald Ford. In 20 years of retirement, Nixon wrote his memoirs and nine other books and undertook many foreign trips, thereby rehabilitating his image into that of an elder statesman and leading expert on foreign affairs. Nixon's onetime opponent George McGovern commented in 1983, 'President Nixon probably had a more practical approach to the two superpowers, China and the Soviet Union, than any other president since World War II [...] With the exception of his inexcusable continuation of the war in Vietnam, Nixon really will get high marks in history.' Political scientist Jussi Hanhimäki disagrees, saying that Nixon's diplomacy was merely a continuation of the Cold War policy of containment by diplomatic, rather than military means.