The 55th Battalion was an infantry battalion of the Australian Army. Raised in 1916 for service during World War I in the AIF the battalion served on the Western Front until the end of the war, before being briefly amalgamated with the 53rd Battalion and then being disbanded in 1919. In 1921, the 55th Battalion (militia) was re-raised and in 1927 adopted the title of the "New South Wales Irish Rifles". This designation was later changed to the "New South Wales Rifle Regiment" in 1930, before they were once again amalgamated with the 53rd, forming the 55th/53rd Battalion (New South Wales Rifle/West Sydney Regiment) in 1937. In October 1941, during World War II, the two militia battalions were delinked and the 55th was later deployed to New Guinea, where they took part in the Kokoda Track ca