The Crater
July 30, 1864
After Cold Harbor, Grant moved his army south of the James and assaulted the weakly held Petersburg defenses from June 15th to 18th. Despite repeated opportunities and overwhelming numbers, Union troops failed to take the city. On June 22nd, the first of many attempts to flank the Confederate defenses failed. As the troops settled down in siege lines, Lt. Col. Henry Pleasants, commanding pre-war miners of the 48th Pa., proposed digging a mine underneath Confederate lines and blowing a hole through enemy lines. Gen. Burnside of the IX Corps choose the black troops of Ferrero's division to be the first wave in an attack through the gap. Confederates suspected a Union mining operation and dug countermines but were unable to locate the Yankees.
Openings of Countermines
Mine Entrance
The Pennsylvanians tunnelled over 500 feet to Rebel lines, the longest mine in military history to that point. This is the entrance, and at the top you can see where the tunnel has caved in. As the mine neared completion, Grant sent Hancock's II Corps and Sheridan's cavalry north of the James to divert Lee's attention. These troops were then brought back to Petersburg with Ord's XVIII Corps from Bermuda Hundred. Sheridan would encircle the Confederates while the infantry would exploit any success. (See West Point map)