The Lower Redoubt was a strong earthen fortification built to protect the Johnsonville depot, overlooking the wharves, warehouses, and the Tennessee River. Union authorities knew the large supply depot was a tempting Confederate target, but army engineers designed the fortification mainly against an infantry attack and ignored the topography of the river’s west bank. That fatal flaw left the gunners unable to lower their cannon enough to hit targets on or near the levee opposite the fort. In November 1864, Confederate Gen. Nathan Bedford Forrest’s chief of artillery recognized this weakness in the depot’s defenses and exploited it.