He volunteered as a trooper in the Second Heavy Cavalry at the outbreak of the First World War and was commissioned in the field after a few months. In the Second Battle of Champagne he was captured by the French and imprisoned in Corté, Corsica. After a failed escape attempt he was punished with solitary confinement in conditions where he contracted tuberculosis. After a spell on a hospital ship, which gave him his first and only glimpse of the Aegean, he was invalided home via Davos in an exchange of prisoners in 1917. Here he was reunited with his English wife Wilhelmine and briefly made the acquaintance of Lenin.