<P> At the start of the war on 1 September 1939 , the Allies consisted of France , Poland and the United Kingdom , as well as their dependent states , such as British India . Within days they were joined by the independent Dominions of the British Commonwealth : Australia , Canada , New Zealand and South Africa . After the start of the German invasion of North Europe until the Balkan Campaign , the Netherlands , Belgium , Greece , and Yugoslavia joined the Allies . After first having cooperated with Germany in invading Poland whilst remaining neutral in the Allied - Axis conflict , the Soviet Union perforce joined the Allies in June 1941 after being invaded by Germany . The United States provided war materiel and money all along , and officially joined in December 1941 after the Japanese attack on Pearl Harbor . China had already been in a prolonged war with Japan since the Marco Polo Bridge Incident of 1937 , but officially joined the Allies in 1941 . </P>
<P> At the start of the war on 1 September 1939 , the Allies consisted of France , Poland and the United Kingdom , as well as their dependent states , such as British India . Within days they were joined by the independent Dominions of the British Commonwealth : Australia , Canada , New Zealand and South Africa . After the start of the German invasion of North Europe until the Balkan Campaign , the Netherlands , Belgium , Greece , and Yugoslavia joined the Allies . After first having cooperated with Germany in invading Poland whilst remaining neutral in the Allied - Axis conflict , the Soviet Union perforce joined the Allies in June 1941 after being invaded by Germany . The United States provided war materiel and money all along , and officially joined in December 1941 after the Japanese attack on Pearl Harbor . China had already been in a prolonged war with Japan since the Marco Polo Bridge Incident of 1937 , but officially joined the Allies in 1941 . </P>
when did the allies enter world war 2
when did the allies enter world war 2
1 September 1939
1 September 1939