Total casualties were light, under 150.
By February 1862, Fort Henry, a small Confederate earthen fort on the Tennessee River with seventeen outdated guns, was partially inundated and the river threatened to flood the rest. Tilghman was working on one weakness of the fort, and had started building Fort Heiman on the high ground across the river. Before he could finish the job, Union troops arrived.
On February 4-5, Gen. Ulysses S. Grant, Union, landed his divisions in two different locations, one on the east bank of the Tennessee River to prevent the garrison’s escape and the other to occupy the high ground on the Kentucky side which would insure the fort’s fall; Foote’s seven gunboats began bombarding the fort. Brig. Gen. Lloyd Tilghman, CSA, realized that it was only a matter of time before Fort Henry fell. While leaving seventy artillerymen in the fort to hold off the Union fleet, he escorted the rest of his force out of the area and sent them safely off on the route to Fort Donelson, 10 miles away. (They escaped since the creeks were too high for Union troops to cut them off.) Tilghman then returned to the fort and, soon afterwards, surrendered to the fleet, which had engaged the fort and closed within 400 yards. (Since the Confederate fort was basically at water level the gunboats could easily and accurately shell it, while a fort on high ground was a harder target and could use plunging fire. Fort Henry was a problem waiting to happen for the South.)
Despite a two-hour gun duel, armor plate saved Foote’s ships from serious damage, and only the USS Essex needed much repair. Fort Henry’s fall opened the Tennessee River to Union gunboats and shipping as far as Muscle Shoals, Alabama. (Foote sent his three wooden gunboats up the almost undefended river, holding his four ironclads to support the attack on Fort Donelson.) After the fall of Fort Donelson, ten days later, the two major water transportation routes in the Confederate west, bounded by the Appalachians and the Mississippi River, became Union highways for movement of troops and material.