In February 1915, the 9th Light Horse Regiment left Melbourne for Egypt, arriving on the 1 February 1915. When the Australian infantry units were dispatched to Gallipoli, it was thought the terrain was unsuitable for mounted troops, and the light horse regiments remained in Egypt. However, heavy casualties resulted in the deployment of the 3rd Light Horse Brigade as reinforcements in May 1915. On arrival, the regiment was attached to the New Zealand and Australian Division. The regiment was the brigade reserve for the battle of the Nek, so did not suffer the same level of casualties as their sister regiments in the brigade, however their first commanding officer, Lieutenant Colonel Albert Miell, was one of those killed. The regiment was involved in the brigade's next attack at Hill 60 on 27 August, which resulted in the death of the replacement commanding officer Lieutenant Colonel Carew Reynell the next day. From then until December 1915, when the regiment was withdrawn, they were only used in a defensive role.