The day before enlisting, he married his girlfriend of three years, Anna Render, a fellow immigrant from Odessa. On August 24, 1914, Schwartzbard and his brother enlisted in the French Foreign Legion. As a legionnaire, he entered the fray in November 1914 and participated in the Second Battle of Artois, near Arras, in May 1915. On account of his excellent military record, in early 1915, he was moved to the regular French 363rd "régiment d’infanterie" and transferred south to the Vosges Forest. While there, he was shot through the left lung, fracturing his scapula and tearing his brachial plexus. The doctors gave him little hope of surviving the wound, but he slowly improved over the next year and a half until he was in good enough shape to return to Russia. His left arm was left virtually useless, and he was awarded the Croix de guerre for his courage in the World War.