Union Military Organisations: Eastern Theatre

Union Military Organisations: Eastern Theatre

Go to Western Territories and Pacific Coast Theatre / Pacific Coast Theatre / Trans-Mississippi, Northwest, and Frontier Theatres / Western Theatre / Gulf Coast Theatre / Capital and North-Eastern Theatre / Atlantic Coast Theatre for detailed summaries.

This theatre broadly covers the states of Virginia, and West Virginia, the District of Columbia, and adjacent operational regions.
Before the war, the Department of the East covered the entire region east of the Mississippi, but it was rapidly diminished as new territorial commands were established in its former territory (e.g., Departments of Florida, Washington, Annapolis, Pennsylvania, Maryland, the Ohio, Virginia, Northeastern Virginia, Kentucky, the Shenandoah, the Potomac, Western Virginia, New England, and several more evolving in the western theatre).
In October 1861, the Department of the East was renamed as the Department of New York, reflecting its reduced scope. It was revived as the Department of the East in January 1863 to manage recruitment and administrative matters, as well as civil disorder. In the meantime, within this reduced theatre, the Department of New England existed briefly from October 1861 to February 1862, primarily as vehicle for recruiting and organising new military forces.
Operations in the eastern theatre were dominated by the fact that the two capitals at Washington, DC, and Richmond, Virginia, were barely one hundred miles apart. Virginia inevitably became a primary theatre of the conflict as each belligerent sought to threaten the other’s capital city while defending its own. Each side had to provide for the defence of its capital, but the urgency was greater on the Union side, tying down large forces to occupy Washington’s extensive fortifications and to counter Confederate diversions and threats. This theatre of command was the constant obsession of the government, press, and people.
The Union had to take the strategic initiative and attempted several overland advances towards Richmond, with occasional efforts made from the coast along the James River and Yorktown Peninsula. The Confederates responded aggressively and made diversionary advances and invasions towards Washington and across the Potomac River into Union territory. This required the Union to make continual adjustments to the military organisation north of the Potomac, which could raise short-term forces, forestall, react to raids, and provide security for the Northern hinterland.
At times Union forces based on either side of the James River synchronised their operations with the main Army of the Potomac, but more frequently they were focused on guarding and extending the garrisons established along the Virginia and North Carolina coasts. They could harass and make diversionary operations, but it was not until Spring 1864 that the integration of overland and coastal operations was accomplished. The primary instrument for action in this sector was the Department of Virginia, initially established on 22 May 1861 only to hold Fortress Monroe but expanding to become a major force. In July 1863 it was merged with the Department of North Carolina into a new Department of Virginia and North Carolina so that operations along the Atlantic coast and rivers in both states could be coordinated more efficiently.
Both sides engaged continually in operations in the Shenandoah Valley and the mountainous region of western Virginia. The Valley was an important source of supplies for the Confederates and offered a covered line of advance into Union territory, an advantage that was exploited effectively in 1862, 1863, and 1864. The general south-westward orientation of the valley meant that any Union advance would gradually diverge and dissipate forces away from the main axis between Washington and Richmond.
Western Virginia was largely pro-Unionist and provided a base for Union operations towards prized natural resources and the vital East-West railroad line through eastern Tennessee and southwestern Virginia. The region was inaccessible to large forces and difficult either to occupy or defend but it constantly drew the attention of both sides. Difficult to conquer and garrison, there were many intense but short campaigns and raids. It was only in late 1864 and early 1865 that the Union forces were able to move in force out of the mountains into eastern Tennessee, southwestern Virginia, and western North Carolina.
The defence of the national capital was always a sensitive issue as its loss would have led to disastrous political and diplomatic consequences. The Department of Washington was founded immediately in April 1861. In July 1861 it was subordinated to the Military Division and then converted into a District of the Department of the Potomac, to ensure that the security of the capital remained an integral responsibility for the main field forces in the eastern theatre. In February 1863, it was reinstated as the Department of Washington with its own Districts established for the defence of, and to provide logistical services around, the capital.
In the immediate crisis of the outbreak of war, short-lived organisations were formed partly in response to immediate or perceived threats and partly to provide a focal point for recruitment and training. These included the Department of Pennsylvania and the Department of the Shenandoah from April to August 1861, and the Department of Annapolis and its successor Department of Maryland from April to July 1861. These were swept away by McClellan as he consolidated centralised command in his Military Division, later Department of the Potomac. The field forces gathered for the first advance into Virginia in the early months of the war were assigned to the Department of Northeastern Virginia on 27 May 1861 as the Army of Northeastern Virginia, and it was clearly differentiated from the capital’s defence force. After the defeat at First Bull Run, in July 1861, the Military Division of the Potomac replaced the Department. In August 1861, the Department of the Potomac, and the Army of the Potomac, which was always the Union’s largest single field force, were created and remained operational until June 1865.

This is an alphabetical Index of each Organisation by Level and then by name 

Details of each specific organisation can be found in the Introduction to Union Military Organisations – Types -by searching for the Level and then the Name of the Organisation

Military Division of the James

Middle Military Division
Military Division of the Potomac

Middle Department
Mountain Department
Department of Northeastern Virginia
Department of the Potomac
Department of the Rappahannock
Department of the Shenandoah #1
Department of the Shenandoah #2
Department of Virginia #1
Department of Virginia #2
Department of Virginia and North Carolina
Department of West Virginia
Department of Western Virginia

District of Alexandria, Virginia
Cheat Mountain District, Virginia #1
Cheat Mountain District, Virginia #2
Cheat Mountain District, Virginia #3
Cheat River District, Virginia
District of Cumberland, Virginia
District of Fort Monroe, Virginia
District of the Gap, Virginia
District of Grafton, Virginia
District of Harper’s Ferry, West Virginia
District of Harper’s Ferry and Cumberland, Virginia
District of Henrico, Virginia
District of the Kanawha, Virginia
District of Lynchburg, Virginia
District of the Northern Neck, Virginia
District of the Nottoway, Virginia
District of Patuxent, Virginia
District of the Peninsula, Virginia
Railroad District, Virginia
District of the Valley of the Big Sandy River, Virginia
District of Virginia #1
District of Virginia #2
District of Eastern Virginia
District of Northeastern Virginia
District of Southwestern Virginia
District of Western Virginia
District of Yorktown, Virginia #1
District of Yorktown, Virginia #2

Sub-District of the Appomattox, Virginia
Sub-District of the Blackwater, Virginia
Sub-District of the Kanawha, Virginia
Sub-District of the Peninsula, Virginia
Sub-District of the Rappahannock, Virginia
Sub-District of Roanoke, Virginia
Sub-District of the South Anna, Virginia
Sub-District of Yorktown, Virginia

Army of the James
Army of the Kanawha
Army of Northeastern Virginia
Army of Occupation
Army of the Potomac
Army of the Shenandoah #1
Army of the Shenandoah #2
Army of the Shenandoah #3
Army of Virginia
Army of West Virginia

Centre Grand Division, Potomac
Left Grand Division, Potomac
Reserve Grand Division, Potomac
Right Grand Division. Potomac

Sheridan’s Cavalry Command Potomac

I Corps Potomac #1
I Corps Potomac #2
I Corps Virginia
II Corps Potomac
II Corps Virginia
III Corps Potomac
III Corps Virginia
IV Corps Potomac
IV Corps Virginia
IV Corps Virginia and North Carolina
V Corps Potomac #1
V Corps Potomac #2
VI Corps Potomac #1
VI Corps Potomac #2
VI Corps Shenandoah
VII Corps Virginia
VII Corps Virginia and North Carolina
VIII Corps Middle
VIII Corps Atlantic
IX Corps Potomac #1
IX Corps Potomac #2
IX Corps Potomac #3
IX Corps Virginia #1
IX Corps Virginia #2
X Corps James
XI Corps Potomac
XII Corps Potomac
XVIII Corps James
XIX Corps Shenandoah
XXIV Corps James
XXV Corps James
Cavalry Corps Potomac
Cavalry Corps Shenandoah