Gatehouse joined the British Army and, after graduating from the Royal Military College, Sandhurst, was commissioned as a second lieutenant into the Northumberland Fusiliers in October 1914 and fought in the First World War.
[4] He was awarded the Military Cross (MC) in September 1918, the citation for which reads: For conspicuous gallantry and devotion to duty while commanding a composite company of twenty Lewis guns.
Under heavy enemy attacks his courage and cheerfulness inspired his men and caused them to hold on to a difficult position under very trying circumstances.
He followed close behind, as they proceeded into action, under heavy shell and machine-gun fire, and superintended their movements in the clearing of two enemy positions.
[9][10] Having led the 10th Armoured Division at the Battle of Alam el Halfa in September 1942 and then the Second Battle of El Alamein in October 1942,[11] he became major general in charge of administration at Washington D.C. at the end of the year, and military attaché in Moscow in 1944 before retiring in 1947.