American Civil War (1861–1865)
Sectional tensions had long existed between the states located north of the Mason-Dixon Line and those south of it, primarily centered on the “peculiar institution” of slavery and the ability of states to overrule the decisions of the national government. During the 1840s and 1850s, conflicts between the two sides became progressively more violent. After the election of Abraham Lincoln in 1860 (who southerners thought would work to end slavery), beginning with South Carolina in late 1860, states in the South seceded from the United States. On April 12, 1861, forces of the South (known as the Confederate States of America or simply the Confederacy) opened fire on Fort Sumter, whose garrison was loyal to the forces of the North (who represented the United States or simply the Union).
The American Civil War caught both sides unprepared. Both the Union and the Confederacy had to build their armies practically from scratch. Both sides sought a quick victory focused on the respective nearby capitols of Washington, D.C. and Richmond, Virginia, but neither side would surrender their national identity cheaply. Even after the First Battle of Bull Run, many were slow to accept that war would last much longer than a single campaign. However, it spilled across the continent, and even to the high seas. Much of the vast resources of America would be consumed before it would be resolved.
The American Civil War is sometimes called the “first modern war” due to the use of mass conscription, military railroads, trench warfare, submarines, ironclads, aerial reconnaissance, modern cartridge firearms, rifles, and machine guns. It introduced the modern world to the horrors of total war.