The Mississippi Army National Guard came into existence under Winthrop Sargent, the first Governor of the Mississippi Territory, with the issuance of an order on 8 September 1798 organizing the Militia of the Territory. On 28 February 1799, Governor Sargent was able to get his legislative body together and the first law was passed for the permanent establishment of the Militia in Mississippi. This law constituted the beginning of the lineage of the 155th Infantry Regiment in Mississippi. The 155th Infantry Regiment is one of only nineteen Army National Guard units with campaign credit for the War of 1812, and the only one from west of the Appalachians. Through the years the laws governing the Militia changed in various ways. Establishment of units varied from year to year, and ways of obtaining strength for the units also varied. There were periods of lack and little Militia at all. At other times the Militia forces were well organized. Although the Mississippi Militia participated in every war and fight of any consequence from the Sabine Expedition of 1806 through the Korean War in 1953, it was not until 1916 the Mississippi National Guard was called for active duty. In 1916 the War Department called three infantry battalions for service on the Mexican Border. These battalions formed the First Infantry Regiment which went on active duty on 24 June 1916. In September 1917 this unit was redesignated the 155th Infantry Regiment and served in the 39th Division in France. Also created during World War I, largely from Arkansas Army National Guard units, was the 154th Infantry Regiment, which continued its service after the war with the Mississippi Army National Guard. Again in 1940 all units of the Mississippi National Guard were inducted into Federal service. Between 1950 and 1951, 77 of 81 units were called into service during the Korean War. A total of 6,515 Mississippi Guardsmen served during this period. Around the early 1960s, the Mississippi Army National Guard had 151 units located throughout the State. 51 of these units were part of the 31st Division and the remainder were non-divisional units. Among units formed within the MS ARNG since World War II are the 198th Armor Regiment, the 114th Field Artillery Regiment, the 185th Aviation Regiment, and the 204th Air Defense Artillery Regiment. For much of the final decades of the twentieth century, National Guard personnel typically served "One weekend a month, two weeks a year", with a portion working for the Guard in a full-time capacity. The current forces formation plans of the US Army call for the typical National Guard unit to serve one year of active duty for every three years of service. More specifically, current Department of Defense policy is that no Guardsman will be involuntarily activated for a total of more than 24 months in one six-year enlistment period. The 1st Battalion, 198th Armor Regiment used to serve as part of the 155th Armoured Brigade, but was disbanded as part of the c.2010 modular reorganization.
Structure
In 2016, the Mississippi Army National Guard included the following units:
