Lacaze served as capitaine de vaisseau in Senegal, India and Viet-Nam. He was naval attaché in Rome and chief of staff to Admiral Germinet. He then took command of the Masséna, before serving as chief of cabinet to minister of the Navy Théophile Delcassé.
During the First World War, Lacaze lead a division of the Mediterranean fleet, and organised part of the Dardanelles Campaign. Lacaze was made Minister of the Navy in October 1915, and he retained the office until 1917. He then went on to serve as préfet maritime of Toulon.