On the commencement of hostilities with Spain, he was promoted to brigadier general of volunteers in May 1898. In Cuba during the war, he commanded one of two cavalry brigades that were part of the Cavalry Division under Major General Joseph Wheeler. Young's brigade included Theodore Roosevelt's Rough Riders, the 1st US Volunteer Cavalry Regiment. In July 1898, after the American victory of the Battle of San Juan Hill, Young assumed command of the Wheeler's Cavalry Division and was made major general of volunteers while he commanded that same division in Cuba after the Santiago Campaign of the Spanish–American War. That same year, Young became a Veteran Companion of the Missouri Commandery of the Military Order of Foreign Wars.