The history of the Arkansas Militia and the Mexican–American War began when the Territory of Arkansas gained admission to the Union as the 25th State on June 15, 1836. Within days the State Governor received a request for troops to relieve federal troops securing the border with Mexico. Ironically the Arkansas National Guard found itself conducting similar missions during the Mexican Expedition of 1916 and again during Operation Jump Start in 2006. Arkansans enthusiastically supported the Mexican–American War in 1846 and many future leaders of the Arkansas Confederate forces gained valuable experience during the conflict. The performance of Arkansas troops during the invasion of northern Mexico and the Battle of Buena Vista did not bring great credit upon the state. Following the Mexican–American War, the state's militia forces again fell into decline until the administration of Governor Elias Nelson Conway, just before the outbreak of the Civil War.