Along with Brigadier General H. Gordon Bennett and others, Mackay received personal congratulations from Field Marshal Sir Douglas Haig. He later received his medals from King George V in a ceremony at Buckingham Palace. Mackay led his battalion once more at the Battle of Broodseinde, earning a fourth mention in despatches. In March 1918, the four machine gun companies in each division were grouped into machine gun battalions. Mackay was given command of the 1st Machine Gun Battalion, the 1st Division's new battalion, which he led in the Battle of Hazebrouck. He was given the brevet rank of major in the 26th Infantry Battalion in the AMF back home on 3 June 1918.