calls for secession. Confederate forces seized numerous federal forts within territory claimed by the Confederacy. A peace conference failed to find a compromise, and both sides prepared for war. The Confederates assumed that European countries were so dependent on " King Cotton " that they would intervene; none did and none recognized the new Confederate States of America. Hostilities began on April 12, 1861, when Confederate forces fired upon Fort Sumter , a key fort held by Union troops in South Carolina. Lincoln called for each state to provide troops to retake the fort; consequently, four more slave states joined the Confederacy, bringing their total to eleven. The Union soon controlled the border states and established a naval blockade that crippled the southern economy. The Eastern Theater was inconclusive in 1861–62. The autumn 1862 Confederate campaign into Maryland (a Union state) ended with Confederate retreat at the Battle of Antietam , dissuading British intervention. [ 6 ] Lincoln issued the Emancipation Proclamation , which made ending slavery a war goal. [ 7 ] To the west, by summer 1862 the Union destroyed the Confederate river navy, then much of their western armies, and the Union siege of Vicksburg split the Confederacy in two at the Mississippi River. In 1863, Robert E. Lee's Confederate incursion north ended at the Battle of Gettysburg . Western successes led to Ulysses S. Grant's command of all Union armies in 1864. In the Western Theater, William T. Sherman drove east to capture Atlanta and marched