In 1940, Field became executive secretary of the American Peace Mobilization (APM), a position for which he had been recruited by Earl Browder himself. "Some time before the APM was formally organized," wrote Field, "Earl Browder asked me if I would accept the executive secretaryship if it were offered me." At APM, Field emerged as a committed pacifist, demanding that the United States stay out of the war in Europe, at least while the Hitler-Stalin pact lasted. His reasoning, as he would explain in his autobiography, was that "the European war in those early stages was one between rival imperialists, the British Empire and the Nazi Reich." By summer of the following year, however, Field came to a complete turnaround: on June 20, 1941, in his capacity as executive secretary, he suddenly called off the organization's "peace picketing" of the White House reversing himself to demand immediate war on Germanyjust two days later, Nazi Germany would launch its surprise invasion of the Soviet Union.