sentences:  With the outbreak of the Mexican–American War, he served under Winfield Scott in the Army of Occupation in Mexico and was brevetted for gallantry in action at the Battle of Cerro Gordo.Following that war, Frost spent part of 1849 as Regimental Quartermaster of an immense supply train sent to the Oregon Territory.The following year he was assigned to Jefferson Barracks in St. Louis, the largest base in the west.