 During their training in the Northern Territory, the members of the 2/12th provided medical support for the 23rd Brigade, participated in the construction of five small medical hospitals, and assisted sappers and pioneer assault units, earning the unit the nickname "2/12th Pioneers".Following the beginning of the Pacific War, 50 members of the 2/12th were each attached to Gull Force and Sparrow Force, and sent to defend the islands of Ambon and Timor respectively.All of the members of the 2/12th serving with Gull Force were captured or killed by the Japanese on 1 February 1942, with many dying as prisoners of war on Ambon or Hainan.