In early 1861 the critical border state of Kentucky had declared neutrality in the American Civil War. This neutrality was first violated on September 3, when Confederate Brig. Gen. Gideon J. Pillow, acting on orders from Maj. Gen. Leonidas Polk, occupied Columbus, Kentucky. The riverside town was situated on 180 foot high bluffs that commanded the river at that point, where the Confederates installed 140 large guns, underwater mines and a heavy chain that stretched a mile across the Mississippi River to Belmont, while occupying the town with 17,000 Confederate troops, thus cutting off northern commerce to the south and beyond.

Two days later, Union Brig. Gen. Ulysses S. Grant, displaying the personal initiative that would characterize his later career, seized Paducah, Kentucky, a major transportation hub of rail and port facilities at the mouth of the Tennessee River. Henceforth, neither adversary respected Kentucky's proclaimed neutrality, and the Confederate advantage was lost. The buffer zone that Kentucky provided between the North and the South was no longer available to assist in the defense of Tennessee.

On February 4 and 5, Grant landed two divisions just north of Fort Henry on the Tennessee River. (The troops serving under Grant were the nucleus of the Union's successful Army of the Tennessee, although that name was not yet in use.) Grant's plan was to advance upon the fort on February 6 while it was being simultaneously attacked by Union gunboats commanded by Flag Officer Andrew Hull Foote. A combination of accurate and effective naval gunfire, heavy rain, and the poor siting of the fort, nearly inundated by rising river waters, caused its commander, Brig. Gen. Lloyd Tilghman, to surrender to Foote before the Union Army arrived.

The surrender of Fort Henry opened the Tennessee River to Union traffic south of the Alabama border. In the days following the fort's surrender, from February 6 through February 12, Union raids used ironclad boats to destroy Confederate shipping and railroad bridges along the river. On February 12, Grant's army proceeded overland 12 miles (19 km) to engage with Confederate troops in the Battle of Fort Donelson.