After the Spanish–American War began in 1898, he was promoted to a captain of volunteers, and served as assistant adjutant general of the 2nd Cavalry Brigade. He received the Medal of Honor for his bravery at the Battle of San Juan Hill near Santiago, Cuba, on July 1, 1898. Though shot through the head, and temporarily blinded, he continued to command his men. He was absent from duty until August 1898 while recovering from the effects of his wounds.