As the two armies faced the stalemate of trench warfare at Petersburg in July 1864, Gen. Ambrose Burnside agreed to a plan suggested by a regiment of Pennsylvania coal miners to dig a mine under the Confederate entrenchments and ignite explosives there to achieve a surprise breakthrough. The mine was detonated on July 30 in what is known as the Battle of the Crater . Because of interference from Meade, Burnside was ordered, only hours before the infantry attack, not to use his division of black troops, which had been specially trained for this mission. He was forced to use untrained white troops instead. He could not decide which division to choose as a replacement, so he had his three subordinate commanders draw lots. The division chosen by chance was that commanded by Brig. Gen. James H. Ledlie, who failed to brief the men on what was expected of them and was reported during the battle to be drunk well behind the lines, providing no leadership. Ledlie's men entered the huge crater instead of going around it, becoming trapped, and were subjected to murderous fire from Confederates around the rim, resulting in high casualties. Burnside was relieved of command on August 14 and sent on leave by Grant; Meade never recalled him to duty.