of Nazi Germany's invasion of Poland. Australia was ill-prepared for war. A National Security Act was passed, the recruitment of a volunteer military force for service at home and abroad was announced, the 2nd Australian Imperial Force, and a citizen militia was organised for local defence. Troubled by Britain's failure to increase defences at Singapore, Menzies was cautious in committing troops to Europe, nevertheless in 1940–41, Australian forces played prominent roles in the fighting in the Mediterranean theatre. A special War Cabinet was created;– initially composed of Menzies and five senior ministers (RG Casey, GA Street, Senator McLeay, HS Gullet and World War I Prime Minister Billy Hughes). In January 1940, Menzies dispatched potential leadership rival Richard Casey to Washington as Australia's first "Minister to the United States". In a consequent by-election, the UAP suffered a heavy defeat and Menzies re-entered coalition negotiations with the Country Party. In March 1940, troubled negotiations were concluded with the Country Party to re-enter Coalition with the UAP. The replacement of Earle Page as leader by Archie Cameron allowed Menzies to reach accommodation. A new Coalition ministry was formed including a number of Country Party members. 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. At the general election in September 1940, there was a large swing to Labor and the UAP-Country Party coalition lost its majority, continuing in office only because of the support of two independent MPs, Arthur Coles and Alexander Wilson. The UAP–Country Party coalition and the Labor parties won 36 seats each. Menzies proposed an all party unity government to break the impasse, but the Labor Party under John Curtin refused to join.