The brigade was initially commanded by a British regular officer, Colonel Ewen Sinclair-Maclagan. After being deployed to Egypt where they undertook further training, the brigade was committed to the fighting in the Gallipoli campaign, being the first Australian unit to land at Anzac Cove on 25 April 1915. They subsequently remained on the peninsula until the end of the campaign in December 1915, taking part in a number of battles including the landing at Suvla Bay and the fighting at Lone Pine and Sari Bair. Following the conclusion of the campaign the brigade was withdrawn and returned to Egypt where a period of reorganisation was undertaken. During this time the AIF was expanded by raising new infantry battalions from cadre personnel drawn from experienced units and bringing in newly trained recruits from Australia. Personnel from the 3rd Brigade were used to raise the 13th Brigade, 4th Division.