During World War II, the Communist Party of Australia was at the height of its influence. The party’s membership peaked at 23,000 in 1944 and it was an influential force in every major trade union. Yet, the stalinisation of the CPA had gutted the party’s internal democracy. In the years leading up to and during the War, it followed every twist and turn of Comintern policy, advocating a “popular front” against fascism (1935-1939), followed by a sharp denunciation of the “imperialist war” (1939-1941) and finally enthusiastic support for the “patriotic war” (1941-1945). In the last phase, the CPA attempted to police industrial militancy in support of the Curtin government’s war effort, in some cases facing defiant resistance. This talk will outline the reasons for and consequences of the CPA’s shifting attitude to the war.