[251]
During a radio broadcast on June 29, 1941, one week after the Nazi invasion of the Soviet Union, Hoover disparaged any "tacit alliance" between the U.S. and the USSR, stating, "if we join the war and Stalin wins, we have aided him to impose more communism on Europe and the world... War alongside Stalin to impose freedom is more than a travesty. It is a tragedy."[252] Much to his frustration, Hoover was not called upon to serve after the United States entered World War II due to his differences with Roosevelt and his continuing unpopularity.[236] He did not pursue the presidential nomination at the 1944 Republican National Convention, and, at the request of Republican nominee Thomas E. Dewey, refrained from campaigning during the general election.[253] In 1945, Hoover advised President Harry S. Truman to drop the United States' demand for the unconditional surrender of Japan because of the high projected casualties of the planned invasion of Japan, although Hoover was unaware of the Manhattan Project and the atomic bomb.