Craven joined the Union Defence Force in 1938 as Director of Physical Education and was sent to Europe to study physical education in Germany, the Netherlands, Belgium, Italy, France, and Britain. The imminent outbreak of war forced the Cravens to return to South Africa. Craven was appointed head of physical education at the South African military academy with the rank of Major. When his section was established as a separate Physical Training Brigade in 1947, Craven was promoted to Lieutenant-Colonel and Director of the brigade. His military career was momentarily interrupted in 1947 as he was appointed lecturer in the Union Education Department at Stellenbosch University before returning to the brigade.