He served in the First World War, at the outset as an enlisted man in the French Army then as an officer in The Royal Canadian Dragoons, and ended the war as an officer in the British Army, serving in Palestine as a major in the 39th Battalion, The Royal Fusiliers (part of the "Jewish Legion").
Ia bertugas dalam Perang Dunia I, masuk Angkatan Darat Prancis, kemudian menjadi perwira dalam The Royal Canadian Dragoons, dan mengakhiri perang tersebut sebagai perwira dalam British Army, menjabat di Palestina sebagai mayor dalam Batalion ke-39, The Royal Fusiliers (bagian dari "Legiun Yahudi").