In the late 1930s, most fellow-travelers broke with the Communist party-line of Moscow when Stalin and Adolf Hitler signed the German–Soviet Non-aggression Pact (August 1939), which allowed the Occupation of Poland (1939–45) for partitioning between the U.S.S.R. and Nazi Germany. In the U.S., the American Communist Party abided Stalin's official party-line, and denounced the Allies, rather than the Germans, as war mongers. In June 1941, when the Nazis launched "Operation Barbarossa", to annihilate the U.S.S.R., again, the American Communist Party abided Stalin's party-line, and became war hawks for American intervention to the European war in aid of Russia, and becoming an ally of the Soviet Union.