With the 1940 election looming, Menzies lost his Chief of the General Staff and three loyal ministers in the Canberra air disaster. The Labor Party meanwhile experienced a split along pro and anti Communist lines over policy towards the Soviet Union for its co-operation with Nazi Germany in the invasion of Poland; this resulted in the formation of the Non-Communist Labor Party. The Communist Party of Australia (CPA) opposed and sought to disrupt Australia's war effort. Menzies banned the CPA after the fall of France in 1940, but by 1941 Stalin was forced to join the allied cause when Hitler reneged on the Pact and invaded the USSR. The USSR came to bear the brunt of the carnage of Hitler's war machine and the Communist Party in Australia lost its early war stigma as a result.