Until the nomenclature changed in the early 1880s, cavalry regiments were organized into companies (later, "troops") authorized at up to 100 men, ten companies made up a regiment (increased to twelve post-war). Two or more companies might be organized into ad hoc battalions (later, "squadrons"), two "wings" of six companies each was used through the Indian Wars. Civil War regiments were rarely near authorized strength so that they were commonly brigaded with two to four other regiments. Two to four brigades were combined into divisions. By the end of the war, 272 cavalry regiments were formed in the Union Army and 137 in the Confederate Army.
Early in the war, most cavalry regiments were dispersed to be under the command of infantry formations, such as divisions or corps, as commanders realized the importance of long-range reconnaissance and raiding, the organizations changed to consolidate more of the regiments into larger units controlled separately. Eventually the Union Army of the Potomac included a Cavalry Corps, which had three divisions, the Army of Northern Virginia, earlier to consolidate under J.E.B. Stuart, organized its force as a cavalry division.
In both armies, the cavalry was accompanied by batteries or battalions of horse artillery, as well as its own train of ammunition and supply wagons.