With the outbreak of the Spanish–American War, Truman volunteered and joined Teddy Roosevelt's Rough Riders, traveling to San Antonio, Texas, where he joined Jim McClintock's company, before traveling on to Tampa, Florida. Shortly before leaving for the war, Truman married Mary Collingwood.[2][5][6] During the war, Truman was one of the first, if not the first, soldiers up the top of the hill during the Battle of San Juan Hill. While in Cuba, Truman contracted malaria, and recuperated in Utica, New York, before returning to Arizona.[7][8][9]
After returning from the war, he served in various political offices including Pinal County assessor, county treasurer, county clerk, as well as serving on the County Board of Supervisors.[4] In 1928 he ran for the single Arizona State Senate seat from Pinal County. He was unopposed in the Democrat's primary, and was won the November general election.[10][11] In September 1929 he was on vacation with his family in California, when he required emergency surgery. He died during the procedure on September 3, in a San Francisco hospital.[2][4]
