- Union Army Regimental Organization
- Union Army Equipping and Training
- Union Army Infantry Battle Tactics
- Union Army Table of Organization
- Major Theaters of the Civil War
- Departments, Divisions, Military Districts and Armies
- The Union Army and the Railroads
- Civil War Fortifications
- Comparing Grant and Lee
- The Confederate States Army Structure and Ranks
The War Department and the Union Army divided operations during the war into major theaters. These were for fixed geographical areas. The armies were generally assigned to those areas but as the war progressed the armies tended to move to the areas of contention rather than remain in pacified areas.
The most prominent and well-known to Civil War enthusiasts are the Eastern Theater and the Western Theater. However, there were four other theaters of the war: the Union Blockade, Lower Seaboard Theater and Gulf Approach, the Trans-Mississippi Theater and the Pacific Coast Theater.
The Eastern Theater of Operations included Virginia, West Virginia, Maryland, and Pennsylvania, the District of Columbia, and the coastal fortifications and seaports of North Carolina. Major campaigns that took place in the Eastern Theater included the Peninsula Campaign, the Seven Days Battles, the Maryland Campaign, the Gettysburg Campaign, the Overland Campaign, the siege of Petersburg and of course, the Appomattox Campaign that substantially ended the war in the Eastern Theater.
The Western Theater of Operations included the area east of the Mississippi River and west of the Appalachian Mountains. It excluded operations against the Gulf Coast and the Eastern Seaboard, but as the war progressed and William Tecumseh Sherman’s Union armies moved southeast from Chattanooga, Tennessee, in 1864 and 1865, the definition of the theater expanded to encompass their operations in Georgia and the Carolinas.
The Union Blockade was a massive effort along the Atlantic and Gulf Coast areas. Its goal was to prevent passage of goods in and out of Southern ports. Based on General Winfield Scott’s “Anaconda Plan”, its goal was to strangle the Confederacy and starve them into submission. It required the Navy to patrol 3,500 miles of coastline and close 12 major ports. The Union Navy built up its forces to 500 ships and captured some 1,500 blockade runners while enforcing the blockade.
The Lower Seaboard Theater encompassed major military and naval operations that occurred near the coastal areas of the Southeastern United States (in Alabama, Florida, Louisiana, Mississippi, South Carolina, and Texas) as well as southern part of the Mississippi River (Port Hudson and south). Inland operations are included in the Western Theater or Trans-Mississippi Theater, depending on whether they were east or west of the Mississippi River. Coastal operations in Georgia, as the culmination of Sherman’s March to the Sea, are included in the Western Theater.
The Trans-Mississippi Theater included major military and naval operations west of the Mississippi River. The National Park Service includes 75 different battles and engagements in this theater. It included Missouri, Arkansas, Texas, Indian Territory (now Oklahoma), Louisiana west of the Mississippi River, Arizona and New Mexico. The Confederates had a mirror image theater that covered the same areas.
Finally, in the Far West was the Pacific Coast Theater. It included operations in California, Oregon, and Nevada, Washington Territory, Utah Territory, and later Idaho Territory. The operations of Union volunteer troop detachments primarily from California, some from Oregon and a few companies from Washington Territory were directed mostly against Indians in the theater. Union and Confederate regular forces did not meet directly within the Pacific Department.