Haking was given command of the 5th Infantry Brigade in September 1911, and took it to the Western Front on the outbreak of war in August 1914, as part of Douglas Haig's I Corps. On 23 August 1914—the day of the Battle of Mons—in accordance with a request by Smith-Dorrien, GOC II Corps, Haig sent Haking with three battalions to make contact with II Corps on Haig's left, but Haking reported back that he had made no contact with the enemy. He helped force the Petit Morin during the Battle of the Marne. During the advance after the Marne, Haking's brigade was at the forefront at the Battle of the Aisne, and on 14 September his was one of the few units to fight its way onto the Chemin des Dames after the crossing of the River Aisne. Haig recorded that Haking's 5th Brigade made good progress on the eastern slopes of the Beaulne ridges, reaching the ridge of Tilleul de Courtacon, before having to pull back on meeting opposition. However, on that day he received a head wound that required three months' recuperation.