Rice then recruited a company which was mustered into service as part of the 26th Missouri Volunteer Infantry, and he served until the end of the war. He took part in all the regiment's battles, including the Siege of Corinth, the Battle of Iuka, the Battle of Missionary Ridge, and Sherman's March to the Sea. He advanced through the ranks to command the regiment with the rank of lieutenant colonel, and he led the unit to St. Louis to be mustered out in the summer of 1865.