The 12th Battalion was an infantry battalion originally raised for the First Australian Imperial Force during the First World War. The battalion was recruited from Tasmania, South Australia and Western Australia and formed part of the 3rd Brigade, 1st Division. It served throughout the war, firstly during the Gallipoli Campaign and then on the Western Front. During the interwar years, the 12th Battalion was re-raised as a part-time military unit and during the Second World War undertook garrison duties in Australia, but did not see combat. Today its lineage is perpetuated by the 12th/40th Battalion, Royal Tasmania Regiment, a unit which continues to serve in the Australian Army Reserve.

The 3rd Brigade is a combined arms brigade of the Australian Army, principally made up of the 1st and 3rd Battalions of the Royal Australian Regiment. Initially raised in 1903 as part of the post-Federation Australian Army, it was removed from the order of battle in 1906 following the restructure of the field force. It was re-formed in 1914 for service during World War I, taking part in the fighting at Gallipoli and on the Western Front in Europe. During World War II the brigade was used in a defensive role before it was disbanded in 1944. It was re-raised in 1967 for service during the Vietnam War and later went on to provide the nucleus of the deployment to East Timor during the Australian-led intervention in 1999. The brigade is currently based at Lavarack Barracks in Townsville, Queensland.