Promoted to colonel in 1913, Chauvel became the Australian representative on the Imperial General Staff but the First World War broke out while he was still "en route" to the United Kingdom. Chauvel arranged for the Australian Imperial Force to be diverted to Egypt, where he joined his new command, the 1st Light Horse Brigade, in December. In May 1915, it was sent dismounted to Gallipoli, where Chauvel assumed responsibility for some of the most dangerous parts of the line. He took charge of the 1st Division that November. In March 1916, Chauvel became commander of the Anzac Mounted Division, gaining victories in the Battle of Romani in August and the Battle of Magdhaba in December, and nearly winning the First Battle of Gaza in March 1917. The following month, he took over the Desert Column, later known as the Desert Mounted Corps, thereby becoming the first Australian to command a corps, and the first to reach the rank of lieutenant general. At Beersheba in October 1917, his light horse captured the town and its vital water supply in one of history's last great cavalry charges. By September 1918, Chauvel was able to effect a secret redeployment of three of his mounted divisions and launch a surprise attack on the enemy that won the Battle of Megiddo. He followed up this victory with one of the fastest pursuits in military history.