Military leadership in the American Civil War was vested in both the political and the military structures of the belligerent powers. The overall military leadership of the United States during the Civil War was ultimately vested in the President of the United States as constitutional commander-in-chief, and in the political heads of the military departments he appointed. Most of the major Union wartime commanders had, however, previous regular army experience. A smaller number of military leaders originated from the United States Volunteers. Some of them derived from nations other than the United States.
In the Southern Confederacy, the constitutional commander-in-chief was educated at West Point and had served in the Mexican War. Many officers in the United States Army, most of them educated at West Point at the expense of the United States, and having taken an oath of allegiance to the same, joined the rebellion against it. Several significant Confederate military leaders emerged from state unit commands. Some military leaders derived from countries other than the United States.