During World War I he joined the Royal Field Artillery as a gunner attached to the 16th Division of Kitchener's Army. Whitcombe saw combat at Hulluch, Guillemont, Messines and Ypres and suffered slight wounds from a machine-gun burst. He was hit by a small piece of shrapnel which became lodged in his left eye—an injury which may have adversely affected his putting in later years. For his war service, he was awarded the British War Medal and the Victory Medal.