With the beginning of the Second World War in 1939, the CPGB initially continued to support the struggle on two fronts (against Chamberlain at home and Nazi fascism abroad). Following the Molotov–Ribbentrop nonaggression pact on August 23 between the Soviet Union and Germany, the Comintern immediately changed its position. The British party immediately fell in line, campaigning for peace, and describing the war as the product of imperialism on both sides, and in which the working class had no side to take.[13] This was opposed within the CPGB by Harry Pollitt and J. R. Campbell, the editor of the Daily Worker, and both were relieved of their duties in October 1939.[14] Pollitt was replaced by Palme Dutt.
From 1939 until 1941 the CPGB was very active in supporting strikes and in denouncing the government for its pursuit of the war.