 During World War II he served as a "Y" (Signals Intelligence) officer in the British Army.From 1941 to 1943 he was assigned to the British Military Mission in Moscow, where he served initially as an Army "Y" specialist and later as the accredited representative of the British "Y" services, rising to the rank of Lieutenant-Colonel.Following a breakdown in "Y" cooperation with the Soviet General Staff in December 1942, the British "Y" Board recalled Crankshaw to London in February 1943.