In May 1897, Smith received his second lieutenant's commission in the Infantry branch. He was assigned to the 12th Infantry Regiment at Fort Niobrara, Nebraska. During the Spanish–American War, Smith served in Cuba with the 12th Infantry. He took part in the Battle of El Caney and the Siege of Santiago. After the war, he received promotion to first lieutenant by brevet in recognition of his gallantry. He received promotion to permanent first lieutenant in March 1899.