At the outbreak of World War II in September 1939, the 37th Battalion was headquartered around Sale, in Victoria, where it formed part of the 10th Brigade. Due to the provisions of the "Defence Act (1903)", which precluded sending the Militia outside Australian territory, initially units such as the 37th Battalion were employed to provide training for personnel called up under the compulsory training scheme, which was reactivated in 1940. As a result, throughout 1940–41, as the Militia were called up to undertake periods of continuous training, the 37th Battalion undertook a number of training camps at Seymour. Following Japan's entry into the war in late 1941, they the units of the 3rd Division were mobilised for war service. In August 1942, however, having remained in Australia carrying out garrison duties and having not been deployed on active service overseas, the battalion was again amalgamated with the 52nd Battalion, this time in response to a manpower shortage in the Australian economy that had been brought about by an over mobilisation of Australia's military forces. At this point the battalion became known as the "37th/52nd Battalion" and initially, it was assigned to the 10th Brigade and attached to the 3rd Division, although it was later transferred to the 4th Brigade in September 1942 after the 10th Brigade was also disbanded. The 37th/52nd was disbanded after the war on 12 June 1946, having fought against the Japanese in the Huon Peninsula and New Britain campaigns.