On this day in 1862, General Ulysses S. Grant finishes a spectacular campaign by capturing Fort Donelson on the Cumberland River in Tennessee. This battle came 10 days after Grant's capture of Fort Henry, just 10 miles to the west on the Tennessee River, and opened the way for Union occupation of central Tennessee.
After Grant surrounded Fort Henry and forced the surrender of 100 men, he moved east to the much more formidable Fort Donelson. The fort sat on a high bluff and had a garrison of 6,000 troops. After the fall of Fort Henry, an additional 15,000 reinforcements were sent to aid Fort Donelson. Grant crossed the narrow strip of land between the two rivers with only about 15,000 troops. One of Grant's officers, Brigadier General John McClernand, initiated the battle on February 13 when he tried to capture a Rebel battery along Fort Donelson's outer works. Although unsuccessful, this action probably convinced the Confederates that they faced a superior force, even though they actually outnumbered Grant.
Over the next three days, Grant tightened the noose around Fort Donelson by moving a flotilla up the Cumberland River to shell the fort from the east. On February 15, the Confederates tried to break out of the Yankee perimeter. An attack on the Union right flank and center sent the Federals back in retreat, but then Confederate General Gideon Pillow made a fatal miscalculation. Thinking he could win the battle, Pillow threw away the chance to retreat from Fort Donelson. Instead, he pressed the attack but the Union retreat halted. Now, Grant assaulted the Confederate right wing, which he correctly suspected had been weakened to mount the attack on the other end of the line.
The Confederates were surrounded, with their backs to the Cumberland River. They made an attempt to escape, but only about 5,000 troops got away. These included Colonel Nathan Bedford Forrest and 500 cavalrymen. Forrest later became a legendary leader in the West and his exploits over the next three years caused much aggravation to the Union Army. When the Rebels asked for terms of surrender, Grant replied that no terms "except unconditional and immediate surrender" would be acceptable. This earned Ulysses S. Grant the nickname "Unconditional Surrender." The loss of Fort Henry and Fort Donelson were unmitigated disasters for the Confederates. Kentucky was lost and Tennessee lay wide open to the Yankees.