After the November 4, 1864, battle at Johnsonville, a much larger fort was needed to protect the supply depot from potential Confederate land attacks. On the hill above the existing Lower Redoubt, labor detachments of United States Colored Troops working alongside various white troops used shovels and pick-axes to build the Upper Redoubt, also called Fort Johnson during the Civil War, in the weeks that followed. Military engineers first surveyed boundaries inside a 3-acre area, then soldiers dug long, deep ditches parallel to the fort's exterior boundaries. A wooden outline, or profile, was built on the ground and raised vertically to simulate the dimensions of the earthwork, and dirt was excavated, thrown back into the framework, and compacted until it filled the profile's dimensions. Days after the battle, Maj. Gen. John M. Scofield, commander of the Union 23rd Corps, was ordered by Brig. Gen. George H. Thomas in Nashville to dispatch two battalions and proceed immediately to Johnsonville to relieve the garrison troops, repair the fire-ravaged supply depot, and prepare for a possible land assault. In only three weeks, much of the Upper Redoubt was completed, with massive earthen walls and the surrounding hillside cleared of trees all the way to the Tennessee River to give the fort's gunners an open field of fire in all directions.