The 45th Battalion was an infantry battalion of the Australian Army. Raised for service during World War I, the battalion served in the trenches on the Western Front in France and Belgium from mid-1916 until the end of hostilities in November 1918. Following this, it was disbanded in May 1919. Later, in 1921, the battalion was re-raised as a part-time unit of the Citizens Force, based in New South Wales. The battalion remained on the order of battle until 1942, when it was merged with the 1st Battalion as part of a force reduction that was undertaken at that time in response to an over mobilisation of the Australian military in the early part of World War II. In 1948, the battalion was re-raised again and remained on the order of battle until 1960 when it was absorbed into the Royal New So