In late October 1864, Brig. Gen. Nathan Bedford Forrest and 3,500 Confederate cavalrymen used Fort Heiman as a base to attack Union supply vessels on the Tennessee River. After placing several artillery pieces along this bluff, Forrest's troopers spent two days sparring with Union vessels. By October 31 they had sunk one steamer, damaged two others, and captured two gunboats. On November 1 Forrest left Fort Heiman and three days later launched one of the most successful raids of the Civil War, attacking the Union supply depot at Johnsonville, Tennessee, some 30 miles south. Before withdrawing to Corinth, Mississippi, Forrest's cavalrymen destroyed four Union gunboats, 14 transports, 20 barges, and 26 pieces of artillery. They also captured 150 Union soldiers and burned nearly $7 million worth of stockpiled supplies bound for Nashville and Union Maj. Gen. George H. Thomas's Army of the Cumberland. Union military supplies brought up the Tennessee River were transferred at Johnsonville Depot from river boats to railcars for shipment to Union-held Nashville, 78 miles to the east. Historic Johnsonville, like Fort Henry, lies beneath the waters of Kentucky Lake. One of the two gunboats captured by Forrest's troopers was the USS Undine, one of the largest tinclads in the Union navy. Forrest armed the Undine and the captured transport Venus with more guns to use against the Union flotilla protecting Johnsonville. Venus was recaptured before the raid; Forrest burned Undine after the raid to prevent its recapture.