In 1890 Crozier was promoted to the rank of captain. During the Spanish–American War he was inspector-general for the Atlantic and Gulf coast defenses. In 1899 he was one of the American delegates to the Peace Conference at the Hague. He later served in the Philippines on the staffs of Generals John C. Bates and Theodore Schwan, and in 1900 was chief of ordnance on the staff of General Adna Chaffee during the China Relief Expedition.