Complex sentence: He graduated from the Saint-Cyr Military Academy in 1900 and joined the French Army, serving in North Africa until he was transferred back to France 1914 when the First World War broke out, when he commanded Zouave troops.
Split into simpler sentences: He graduated from the Saint-Cyr Military Academy in 1900 and joined the French army. He served in North Africa until he was transferred back to France 1914 when the First World War broke out and commanded Zouave troops.