It was originally intended that the battalion would land in the Middle East; however, the strategic situation in Europe at the time resulted in it being diverted to the United Kingdom where it formed part of Australia's contribution to the defence of the island during a period when an invasion seemed likely. When this threat passed, the 2/12th was sent to North Africa, and in 1941 it took part in the defence of Tobruk and then undertook garrison duties in Syria, before returning to Australia in early 1942. In August 1942, the battalion fought in the Battle of Milne Bay, turning back a Japanese invasion force there, before capturing Goodenough Island before returning to Australia in early 1943. The 2/12th returned to New Guinea in August 1943, and subsequently took part in the Finisterre Range campaign into early 1944. Its final campaign came in mid-1945 when it was committed to re-capturing Borneo, landing on Balikpapan in July 1945. It was disbanded in January 1946.