Spanish–American War
In 1898, Wheeler, now aged 61, volunteered for the Spanish–American War, receiving an appointment to major general of volunteers from President William McKinley. He assumed command of the cavalry division, which included Theodore Roosevelt's Rough Riders, and was nominally second-in-command of the Fifth Army Corps. He sailed for Cuba and was charged with scouting for the U.S. advance by General William Rufus Shafter, overall commander of V Corps. He was ordered not to engage the enemy on his own until the American troop disembarkation had been completed.
Approaching Las Guasimas de Sevilla on June 24, American reports suggested the Spaniards were digging in with a field gun; however, Cuban scouts contradicted these, revealing the Spaniards were preparing to abandon their position. In fact, the Spanish troops at the position had received orders to fall back on Santiago. Wheeler requested the assistance of the attached Cuban forces in an immediate attack, but their commander, Col. Gonzales Clavel, refused. Wheeler attacked anyway, rushing his men forward with two guns to the front. Colonel Young's brigade led the advance against the Spanish columns in what came to be called the Battle of Las Guasimas, the first major engagement of the war.
During the excitement of the battle, Wheeler is said to have called out, "Let's go, boys! We've got the damn Yankees on the run again!" Wheeler's forces moved to encircle the Spaniards' first battle line, assaulting its front and right flank, but were repelled. During a pause in the fighting, both sides reinforced their positions. The Spaniards sent forward two companies of the San Fernando Battalion, along with the artillery. After midday, the U.S. attack was renewed, but Spanish Comandante Andrés Alcañiz, leading the Provisional de Puerto Rico Battalion, once again checked the American assault.
After halting the American advance, the Spanish resumed their ongoing withdrawal toward Santiago's outer defenses according to their original plans. The battle had cost U.S. forces 17 dead and 52 wounded, while Spanish forces suffered seven dead and seven wounded.
Wheeler fell seriously ill during the campaign and turned over command of the division to Brig. Gen. Samuel S. Sumner. Wheeler was still incapacitated in July when the Battle of San Juan Hill began, but once he heard the sound of guns, the "War Child" returned to the front despite his illness. Being the senior officer at the front, he first issued orders to the 1st Division, under Jacob F. Kent, before returning to his own command. Upon taking the heights, Wheeler assured General William R. Shafter that the position could be held against a counterattack. He led the division through the Siege of Santiago and was a senior member of the peace commission.
Wheeler's youngest son died shortly after his return from serving in Cuba; he drowned while swimming in the ocean. When back in the United States, Wheeler commanded the convalescent camp of the army at Montauk Point, now a state park in New York.
