On December 20, 1860, shortly after Abraham Lincoln's victory in the presidential election of 1860, South Carolina declared its secession from the United States and, by February 1861, six more Southern states had adopted similar ordinances of secession. The seven states adopted a provisional constitution for the Confederate States of America and established their temporary capital at Montgomery, Alabama. Shortly after, South Carolina demanded that the U.S. Army abandon its facilities in Charleston Harbor. On December 26, 1860, Major Robert Anderson of the U.S. Army surreptitiously moved his small command from the vulnerable Fort to Fort Sumter, but the Confederate siege prevented any supplies from coming in, and Anderson was forced to evacuate the fort and surrender it to the Confederates. Less than a year later, on July 21, 1861, Union and Confederate armies clashed near Manassas Junction, Virginia, in the first major land battle of the American Civil War. Known as the First Battle of Bull Run, the engagement began when about 35,000 Union troops marched from the federal capital in Washington, D.C. to strike a Confederate force of 20,000 along a small river known as Bull Run. After fighting on the defensive for most of the day, the rebels rallied and were able to break the Union right flank, sending the Federals into a chaotic retreat towards Washington. The Confederate victory gave the South a surge of confidence and shocked many in the North, who realized the war would not be won as easily as they had hoped.