Alexander returned to the Western Front in August 1915, fought at the Battle of Loos and was, for ten days in October 1915, an acting major and acting Commanding Officer (CO) of the 1st Battalion, Irish Guards, as a "Battle Casualty Replacement". He then returned to the 2nd Battalion as a company officer and, in January 1916, received the Military Cross for his bravery at Loos. For service in the Battle of the Somme on 15 September 1916, he was, in October, appointed to the Distinguished Service Order (DSO), the citation for which read: "For conspicuous gallantry in action. He was the life and soul of the attack, and throughout the day led forward not only his own men but men of all regiments. He held the trenches gained in spite of heavy machine gun fire." In the same month, Alexander was further honoured with induction into the French Légion d'honneur.