Fort Sumter, located on an island in Charleston Harbor, with its 90-man garrison commanded by Maj. Robert Anderson, was besieged by the Confederates late in December 1860. Anticipating a Union attempt to reinforce the Garrison, Brig. Gen. Pierre G. T. Beauregard, commander of Confederate forces in the Charleston area, demanded the surrender of the fort on 11 April 1861. Anderson rejected the demand. On the following morning Confederate batteries ringing the harbor began a heavy 34-hour bombardment of the fort. The Federal garrison vigorously returned the fire, but the result was inevitable. Anderson surrendered on 13 April with the honors of war, and was permitted to evacuate his command by sea on the following day.
After Sumter both sides energetically raised troops and prepared for war. Northern public opinion demanded immediate action, preferably an advance against Richmond, and the Confederate moves to defend the approaches to that city assumed the appearance of an intention to attack Washington.