Fort Henry was an important part of the Confederate defensive line in northern Tennessee at the start of the American Civil War. It was meant to block the Tennessee River, preventing Union forces from using it to enter the heart of the state. However, it was a truly terrible fort, built on low ground that was prone to flood whenever the river rose, and overlooked by high ground. The Confederate garrison was only 2,500 strong, nowhere near strong enough to defend the fort against any determined attack.
That determined attack was launched by U. S. Grant, at this point the commander of the Federal forces at Cairo, where the Ohio and Mississippi Rivers meet. From Cairo, Grant saw that he could use the Ohio River to attack Fort Henry on the Tennessee River and Fort Donelson on the Cumberland River. Grant proposed to move 15,000 men along the rivers to Fort Henry, supported by a flotilla of the river navy under Andrew Foote. His plan was eventually approved by General Halleck at the end of January.
The attack did not go as planned. Grant landed his men several miles downstream from Fort Henry, with the intention of attacking the fort from the rear while the gunboats bombarded it from the river. Heavy rain meant that Grant’s men made slow progress. The same rain flooded the lower levels of Fort Henry. On the morning of 6 February, Foote’s gunboats found themselves attacking the fort without infantry support. However, the terrible design of the fort meant that only nine Confederate guns could actually fire on the fleet. The commander of the fort recognised that his position was hopeless. Accordingly, he sent the bulk of the 2,500 strong garrison on the short cross-country journey to Fort Donelson, leaving an artillery company to fight it out with the gunboats.
The artillery duel continued for two hours, before the Confederate artillerymen were overwhelmed. They surrendered to the gunboat fleet before Grant’s infantry even appeared on the scene. The loss of Fort Henry shattered the Confederate line in Tennessee. Three of Foote’s gunboats continued south along the Tennessee River, reaching as far as Alabama, capturing nine Confederate ships and destroying a key railroad bridge. Meanwhile, Grant was already turning towards Fort Donelson.