However he was recalled from retirement to serve in World War I in 1914 and held command on the Western Front, taking part in the Battle of Loos in 1915, the capture of Gommecourt on the first day of the Battle of the Somme in 1916, and was Commander R.E. of the 46th Division when it broke the Hindenburg Line in 1918.
As part of General Sir Edmund Allenby's Third Army, the 46th Division was involved in the diversion at Gommecourt on the first day on the Somme, 1 July 1916.
The victorious German troops who defended the village during the battle were the 52nd Infantry Division from Baden together with 2nd Guards Reserve Division from Westphalia; the British Army force taking part in the attack comprised the 56th (London) Division and the 46th (North Midland) Division.
He fell in action at the opening of the Battle of the Somme offensive on 1 July 1916 during the assault by the 56th (London) Division at Gommecourt.
In May 2006, a book by MacCormick was published under the pen name Alan MacDonald, Pro Patria Mori: The 56th (1st London) Division at Gommecourt, 1st July 1916.