Union Organisations – Military Divisions

Union Organisations – Military Divisions

Military Divisions were strategic commands, reporting directly to the President and War Department. They were devised to coordinate the operations of their subordinate Departments at a strategic level.
The first Military Division (The Potomac) was designated in 1861 but this was no larger than a Department and devised primarily to bring the hastily organised commands in and around the capital district under unified command. The Military Division was disbanded as soon as new Departments had been formed on a more logical basis.
In Spring 1862, the Department of the Mississippi had operated rather like a Military Division with authority over a group of western Departments because they shared a single overall commander. However, this nominal coordination had little impact on the effectiveness of its divergent commands.
Apart from these experiments, the highest-level of territorial command remained the Department until the Military Division of the Mississippi was created in October 1863. This was the first time that a unified strategic command over more than one Department was properly and effectively asserted.
More Military Divisions were established late in 1864 and this proved to be a valuable innovation to coordinate campaigns across extensive territories in the west.
By 30 April 1865, after the end of significant hostilities, there were four Military Divisions, controlling fourteen subordinate Departments. There were also five autonomous Departments.
By the end of June 1865, every Department had been subordinated to one of the restructured Military Divisions. Thus, after the war, the entire territory of the United States was assigned to a Military Division.

Alphabetical List

Military Division of the Atlantic 27 June 1865-31 December 1865
Military Division of the Gulf 27 June 1865-31 December 1865
Military Division of the James 19 April 1865-27 June 1865
Middle Military Division 7 August 1864-27 June 1865
Military Division of the Mississippi 16 October 1863-31 December 1865
Military Division of the Missouri 30 January 1865-27 June 1865
Military Division of the Pacific 27 June 1865-31 December 1865
Military Division of the Potomac 25 July 1861-17 August 1861
Military Division of the Southwest 17 May 1865-27 June 1865
Military Division of the Tennessee 27 June 1865-31 December 1865
Military Division of West Mississippi 7 May 1864-17 May 1865

Chronological List (by date of establishment)

Military Division of the Potomac
25 July 1861-17 August 1861
George Brinton McClellan 25 July 1861-17 August 1861
25 July 1861: The Military Division of the Potomac was established, comprising the Department of Washington and the Department of Northeastern Virginia.
17 August 1861: The Military Division of the Potomac was discontinued.

Military Division of the Mississippi
16 October 1863-31 December 1865 and continuing
Ulysses Simpson Grant 16 October 1863-18 March 1864
William Tecumseh Sherman 18 March 1864-31 December 1865
16 October 1863: The Military Division of the Mississippi was established to comprise the Department of the Ohio, the Department of the Cumberland, and the Department of the Tennessee. The Department of the Tennessee was subordinated to the Military Division of the Mississippi. The Department of the Cumberland was subordinated to the Military Division of the Mississippi. The Department of the Ohio was subordinated to the Military Division of the Mississippi.
29 October 1864: Cavalry Corps Mississippi was established in the Military Division of the Mississippi.
7 November 1864: The “Army of Georgia” was established unofficially in the Military Division of the Mississippi.
24 November 1864: The Department of the Tennessee was nominally discontinued, and its territory transferred to the Military Division of the Mississippi; the Department was effectively discontinued from 28 November 1864 when its constituent territorial commands transferred to the Department of the Mississippi.
28 November 1864: The Department of the Tennessee was discontinued and its territory transferred to the Military Division of the Mississippi.
17 January 1865: The Department of the Ohio was discontinued, and its territory was incorporated into the Department of the Cumberland.
31 January 1865: The Department of North Carolina was established and was subordinated to the Military Division of the Mississippi.
28 March 1865: The Army of Georgia was officially established and confirmed.
17 April 1865: Cavalry Corps Military Division of the Mississippi was discontinued.
19 April 1865: The parts of North Carolina not occupied by the armies of the Military Division of the Mississippi transferred from the Department of North Carolina to the Military Division of the James.
17 June 1865: The Army of Georgia was discontinued. XIV Corps Georgia transferred from the Army of Georgia to the Military Division of the Mississippi.
27 June 1865: The Department of North Carolina transferred from the Military Division of the Mississippi to the Military Division of the Atlantic. The Military Division of the Mississippi was reorganised to consist of the Department of the Ohio, the Department of the Missouri, and the Department of Arkansas. The Army of the Cumberland was subordinated to the Military Division of the Mississippi. The Department of the Cumberland was discontinued. The Department of Kentucky transferred from the Military Division of the Mississippi to the Military Division of the Tennessee.
1 August 1865: The Department of Arkansas was discontinued. The Army of the Cumberland was discontinued. The Army of the Tennessee was discontinued. The Army of Arkansas was discontinued. VII Corps Arkansas was discontinued.

Middle Military Division
7 August 1864-27 June 1865
Philip Henry Sheridan 7 August 1864-27 February 1865
Winfield Scott Hancock 27 February 1865-28 February 1865,
Alfred Thomas Archimedes Torbert interim 28 February 1865
Winfield Scott Hancock 28 February 1865-27 June 1865
7 August 1864: The Middle Military Division was established, comprising the Department of Washington, the Department of the Susquehanna, the Middle Department, and the Department of West Virginia. The Middle Department transferred to the Middle Military Division. The Department of the Susquehanna transferred to the Middle Military Division. The Department of Washington transferred to the Middle Military Division. The Department of West Virginia transferred to the Middle Military Division. The Army of the Shenandoah was established in the Middle Military Division.
21 September 1864: The Department of the Susquehanna was discontinued, and its territory was transferred to the Department of Pennsylvania. The Department of Pennsylvania was established in the Middle Military Division, comprising the state of Pennsylvania and the counties of Columbiana, Belmont, and Jefferson counties of Ohio.
17 May 1865: VIII Corps Middle transferred from the Middle Department to the direct command of the Middle Military Division.
27 June 1865: The Department of Pennsylvania was discontinued, and its territory was divided between the Middle Department and the Department of the Ohio. The Department of the Potomac was discontinued, and its territory was incorporated into the Middle Department. The Middle Department transferred to the Military Division of the Atlantic. The Department of Washington transferred to the Military Division of the Atlantic. The Department of West Virginia was discontinued, and its territory was divided between the Middle Department and the Department of the Ohio. VIII Corps Middle transferred to the Military Division of the Atlantic. The Middle Military Division was discontinued and its territory was incorporated into the Military Division of the Atlantic.

Military Division of the Missouri
30 January 1865-27 June 1865
John Pope 30 January 1865-27 June 1865
30 January 1865: The Military Division of the Missouri was established. It included the Department of the Northwest and the Department of the Missouri. The Department of the Northwest transferred to the Military Division of the Missouri. The Department of the Missouri transferred from the Military Division of West Mississippi to the Military Division of the Missouri.
16 February 1865: Montana Territory and the part of Dakota Territory west of 100 degrees longitude transferred from the Department of the Northwest to the Department of the Missouri.
17 February 1865: The District of Utah transferred from the Department of the Pacific to the Department of the Missouri.
21 March 1865: The Department of Arkansas transferred from the Military Division of West Mississippi to the Military Division of the Missouri.
17 May 1865: The Department of Arkansas transferred from the Military Division of the Missouri to the Military Division of the Southwest.
27 June 1865: The Department of the Northwest was discontinued, and its territory incorporated into the Department of the Missouri. The Department of the Missouri transferred to the Military Division of the Mississippi. The Military Division of the Missouri was discontinued.

Military Division of the James
19 April 1865-27 June 1865
Henry Wager Halleck 19 April 1865-27 June 1865
19 April 1865: The Military Division of the James was established to comprise the Department of Virginia and the Department of the Potomac. The Department of the Potomac transferred to the Military Division of the James. The Department of Virginia transferred to the Military Division of the James. The parts of North Carolina not occupied by the armies of the Military Division of the Mississippi transferred from the Department of North Carolina to the Military Division of the James.
27 June 1865: The Department of the Potomac was discontinued. The Department of Virginia transferred from the Military Division of the James to the Military Division of the Atlantic. The Military Division of the James was discontinued and its territory was incorporated into the Military Division of the Atlantic.

Military Division of West Mississippi
7 May 1864-17 May 1865
Edward Richard Sprigg Canby 7 May 1864-3 November 1864
Joseph Jones Reynolds temporary 4 November 1864-23 November 1864
Edward Richard Sprigg Canby 24 November 1864-17 May 1865
7 May 1864: The Military Division of West Mississippi was established, comprising the Department of the Gulf and the Department of Arkansas. It was also known as the Trans-Mississippi Military Division. The Department of Arkansas transferred to the Military Division of West Mississippi. The Department of the Gulf transferred to the Military Division of West Mississippi.
27 May 1864: The Department of the Missouri transferred to the Military Division of West Mississippi.
28 November 1864: The Department of the Mississippi was established and subordinated to the Military Division of West Mississippi. It comprised the state of Mississippi and the parts of Tennessee west of the Tennessee River taken from the discontinued Department of the Tennessee.
10 February 1865: The District of Key West and Tortugas was detached from the Department of the Gulf to report directly to the Military Division of West Mississippi.
18 February 1865: The Army of West Mississippi was established in the Military Division of West Mississippi.
1 March 1865: The District of West Florida and South Alabama transferred from the Department of the Gulf to the direct control of the Military Division of West Mississippi. The Sub-District of West Florida transferred with the District of West Florida and South Alabama from the Department of the Gulf to the Military Division of West Mississippi.
17 March 1865: The District of West Florida and South Alabama was discontinued. Its territory transferred from the Military Division of West Mississippi to the Department of the Gulf as the new District of West Florida and the District of South Alabama.
21 March 1865: The Department of Arkansas transferred from the Military Division of West Mississippi to the Military Division of the Missouri.
17 May 1865: The Military Division of West Mississippi retained interim responsibility for the Army of West Mississippi and the Army of the Gulf. The Department of the Gulf was separated from the authority of the discontinued Military Division of West Mississippi and became temporarily autonomous, pending transfer to the Military Division of the Southwest. It took responsibility for Mississippi, Alabama, and Florida. The District of Key West and Tortugas was discontinued, and its territory was assigned to the Department of the Gulf. The Military Division of West Mississippi was officially discontinued but remained in interim existence, pending transfer to the Military Division of the Southwest until finally disbanded officially on 1 June 1865.

Military Division of the Southwest
17 May 1865-27 June 1865
Edward Richard Sprigg Canby interim 17 May 1865-5 June 1865
17 May 1865: The Military Division of the Southwest was established, to comprise the Department of Arkansas, the Department of the Gulf. and the Department of Texas. The states of Louisiana and Texas were detached from the Department of the Gulf and assigned to the Military Division of the Southwest.
23 May 1865: XXV Corps Southwest transferred from the Army of the James to the Military Division of the Southwest.
1 June 1765: The Army of West Mississippi transferred from the Military Division of West Mississippi to the Military Division of the Southwest.
3 June 1865: The Army of the Gulf transferred from the Army of West Mississippi to the Department of the Gulf. The Army of West Mississippi was discontinued.
4 June 1865: XXV Corps Southwest was discontinued.
5 June 1865: The Department of the Mississippi was discontinued. The Military Division of West Mississippi was finally disbanded after being officially discontinued on 17 May 1865.
27 June 1865: The Department of Arkansas transferred from the Military Division of the Southwest to the Military Division of the Mississippi. The Department of the Gulf was discontinued, and its territory incorporated into the Department of Louisiana, the Department of Mississippi, the Department of Alabama, the Department of Florida, and the Department of Texas. The Military Division of the Southwest was discontinued.

Military Division of the Atlantic
27 June 1865-31 December 1865 and continuing
George Gordon Meade 27 June 1865-31 December 1865
27 June 1865: The Military Division of the Atlantic was established. It included the Department of the East, the Department of Virginia, the Department of North Carolina, the Department of South Carolina, and the Middle Department. The Army of the Potomac transferred from the Department of the Potomac to the Military Division of the Atlantic. The Department of South Carolina was established and subordinated to the Military Division of the Atlantic. The Department of the East was subordinated to the Military Division of the Atlantic. The Middle Department transferred from the Middle Military Division to the Military Division of the Atlantic. The Department of North Carolina transferred from the Military Division of the Mississippi to the Military Division of the Atlantic. The Department of Virginia transferred from the Military Division of the James to the Military Division of the Atlantic. The Department of Washington transferred from the Middle Military Division to the Military Division of the Atlantic.
28 June 1865: The Army of the Potomac was discontinued. The Army of the James transferred from the Department of Virginia to the Military Division of the Atlantic.
1 August 1865: The Army of the James was discontinued.

Military Division of the Gulf
27 June 1865-31 December 1865 and continuing
Edward Richard Sprigg Canby interim 27 June 1865-5 June 1865
Philip Henry Sheridan 17 May 1865-31 December 1865
27 June 1865: The Military Division of the Gulf was established. It included the Department of Florida, the Department of Mississippi, the Department of Louisiana, and the Department of Texas. The Department of Florida was established in the Military Division of the Gulf. The Department of Louisiana was established in the Military Division of the Gulf. The Department of Mississippi was established in the Military Division of the Gulf. The Department of Texas was established in the Military Division of the Gulf.
7 October 1865: The Department of Mississippi transferred from the Military Division of the Gulf to the Military Division of the Tennessee.

Military Division of the Pacific
27 June 1865-31 December 1865 and continuing
Henry Wager Halleck 27 June 1865-31 December 1865
27 June 1865: The Military Division of the Pacific was established, comprising the Department of California and the Department of the Columbia.
27 June 1865: The Department of California was established in the Military Division of the Pacific. The District of Arizona transferred from the Department of the Pacific to the Department of California.  The Department of the Columbia was established in the Military Division of the Pacific.

Military Division of the Tennessee
27 June 1865-31 December 1865 and continuing
George Henry Thomas 27 June 1865-31 December 1865
27 June 1865: The Military Division of the Tennessee was established. It comprised the Department of Tennessee, the Department of Kentucky, the Department of Alabama, and the Department of Georgia. The Department of Alabama was established in the Military Division of the Tennessee. The Department of Kentucky transferred from the Military Division of the Mississippi to the Military Division of the Tennessee. The Department of Tennessee was established in the Military Division of the Tennessee. The Department of Georgia was established in the Military Division of the Tennessee.
7 October 1865: The Department of Mississippi transferred from the Military Division of the Gulf to the Military Division of the Tennessee.