 On the outbreak of World War I in 1914, he joined the British Army, from which he transferred to the Royal Flying Corps as a pilot, in 1915.He fought in the skies over the Western Front in France and Belgium, and during 1916–17 he returned to South Africa on recruiting tours for the RFC.He recruited more than 8,000 volunteers, of whom 2,000 were accepted, most of them as pilots.