From 1881 to 1897, Charles McCawley worked as Chief Clerk in the office of the Commandant of the Marine Corps, during the last two years of which the Commandant was his own father, Colonel Charles G. McCawley, the 8th Commandant of the Marine Corps. On the day his father retired, he received a direct appointment in the Marine Corps with the rank of Captain, and subsequently served in Cuba during the Spanish-American war, earning the Brevet Medal. As a Brigadier General he served as the Quartermaster of the Marine Corps during World War I. In that position, he visited the front-line troops in the fall of 1918 to learn first-hand of the needs of the men in the field, earning the Navy Distinguished Service Medal. He retired as a Marine Corps Brigadier General in 1929 at the age of 64.