With the outbreak of the Second World War once again the government made the decision to form an overseas expeditionary force outside of the pre-existing Militia units. In order to maintain the ability of the Army to defend Australia should Japan enter the war, it was decided once again to limit the number of militiamen that were allowed to enlist in the Second Australian Imperial Force (2nd AIF) to roughly one quarter. While the units of the 2nd AIF were sent overseas to England, North Africa and the Middle East, the militia remained in Australia to carry out various garrison duties and training in order to improve the nation's overall readiness. Following Japan's entry into the war in December 1941 this changed and over the course of 1942–45 many Militia units were mobilised and deployed to fight in New Guinea, New Britain, Bougainville and Borneo. In any case over 207,000 militiamen transferred from the Militia to the AIF throughout the course of the war. As a result of this, and the serious manpower shortages experienced by the Australian economy from October 1942 onwards eight Militia battalions were disbanded while another eleven more were broken up and their personnel distributed to other units. The 1st/45th Battalion was one of the battalions that were disbanded, doing so in 1944 having not deployed overseas. Prior to this, though, the battalion was reorganised in August 1942 with its machine gun company being transferred to form the 6th Machine Gun Battalion along with several other Militia machine gun companies.