Initially, the battalion concentrated at Randwick, Sydney, forming the 1st Brigade along with the 1st, 2nd and 3rd Battalions. After only two months training the battalion was among the first Australian units to be deployed overseas, arriving in Egypt on 2 December 1914. After this the battalion undertook further training and took part in the defence of the Suez Canal before taking part in the Landing at Anzac Cove on 25 April 1915 as part of the second and third waves. The following day, its commanding officer, Lieutenant Colonel Astley Thompson, who had only just taken over from the adjutant Captain Iven Mackay who had been commanding the battalion temporarily in Thompson's absence, was killed in action. In August, the battalion took part in the attack on Lone Pine after which they were involved in the defensive stalemate that ensued until they were evacuated from the peninsula along with the rest of the force in December 1915.