Both sides raised large volunteer and conscription armies. The states that remained loyal to the federal government were known as the Union. states in February 1861), and asserted claims to two more. The Confederacy grew to control at least a majority of territory in eleven states (out of the 34 U.S. Fighting broke out in April 1861 when the Confederate army began the Battle of Fort Sumter in South Carolina, just over a month after the first inauguration of Abraham Lincoln.

The last minute Crittenden Compromise tried to avert conflict but failed both sides prepared for war. Confederate forces seized federal forts within territory they claimed. An initial seven Southern slave states declared their secession from the country to form the Confederacy. Disunion came after Abraham Lincoln won the 1860 United States presidential election on an anti-slavery expansion platform. Decades of political unrest over slavery led up to the war. The practice of slavery in the United States was one of the key political issues of the 19th century. On the eve of the Civil War in 1860, four million of the 32 million Americans (~13%) were enslaved black people, almost all in the South. The central cause of the war was the status of slavery, especially the expansion of slavery into territories acquired as a result of the Louisiana Purchase and the Mexican–American War. The American Civil War (Ap– May 9, 1865) (also known by other names) was a civil war in the United States fought between the Union (states that remained loyal to the federal union, or 'the North') and the Confederacy ( states that voted to secede, or 'the South').

Napoleon total war north and south