 Upon formation, the AIF consisted of only one infantry division, the 1st Division, and the 1st Light Horse Brigade.The 1st Division was made up of the 1st Infantry Brigade under Colonel Henry MacLaurin; the 2nd, under Colonel James Whiteside McCay, an Australian politician and former Minister for Defence; and the 3rd, under Colonel Ewen Sinclair-Maclagan, a British regular officer seconded to the Australian Army before the war.The 1st Light Horse Brigade was commanded by Colonel Harry Chauvel, an Australian regular, while the divisional artillery was commanded by Colonel Talbot Hobbs.