In the hours following the September 29, 1864, Federal triumph at Fort Harrison, 1,000 yards south of here, Confederate defenses stiffened. Two hundred Georgia infantrymen and Virginia artillerists filled Fort Johnson. Later in the morning they repulsed a direct attack launched by the 2nd Pennsylvania Heavy Artillery, a large unit converted to infantry service. The treeless plain in front of the fort gave the Confederates an excellent field of fire. Fort Johnson became the northern anchor of a new Confederate line, built to cover the gap created by the loss of Fort Harrison.
Confederate engineers employed defensive methods that were both centuries-old (sharpened stakes-abatis) and futuristic (land mines).
Their land mines, known then as torpedos, were artillery shells with special fuses designed to explode on contact. At Fort Johnson, and along the rest of the Confederate line, the mines were buried every two to five feet.