Before dawn on 30 July 1864 Union soldiers set off a mine they had dug under a Confederate salient at Petersburg, Virginia, blasting a crater in the enemy line. The attack that followed fell apart: unit after unit went into the crater instead of around it, and a Confederate counterattack under General William Mahone sealed the gap. After hours of fighting the Union lost about 3,800 men, many of them Black soldiers of the U.S. Colored Troops. A chance to end the siege of Petersburg was gone.
A tunnel under the lines
By late June 1864 the armies of Ulysses S. Grant and Robert E. Lee faced each other in trenches east of Petersburg, and neither side was ready to risk an attack. At one point the picket line of Major General Ambrose E. Burnside's IX Corps lay only about four hundred feet from a Confederate strongpoint, called Elliott's Salient by the Petersburg battlefield park and Pegram's Salient in the Park Service's battle summary. According to the American Battlefield Trust, some of Burnside's men were Pennsylvania miners, and they proposed to tunnel under the salient and blow it up; Grant was doubtful, but the digging began.1
The aim, as the National Park Service puts it, was to surprise and overwhelm the Confederates, seize the heights above Petersburg and so shorten the siege.2
Into the crater
After weeks of preparation the mine was exploded at about 4:45 on the morning of 30 July. Contemporary accounts, the Park Service notes, describe a hole 170 feet long, 60 feet wide and 30 feet deep in places. The blast tore a gap about 200 feet wide in the Confederate line, and the Union sent in unit after unit. Poorly led, many of them went down into the crater instead of around it, and once there they could neither advance nor easily retreat, because Confederate artillery and infantry turned both directions into killing fields.3
The IX Corps's Fourth Division, made up of regiments of the U.S. Colored Troops under Ferrero, went in last; in its first battle it advanced farther than any other Union unit. Then Mahone's counterattack drove it back and plugged the gap. At 9:30 Burnside received orders to call off the attack, but according to the Park Service the men in the crater did not learn of it until 12:30. Around one in the afternoon the Confederates rushed the crater itself, in the fiercest hand-to-hand fighting of the whole siege, and the Union soldiers there surrendered. The Park Service records that as prisoners were taken to the rear, unarmed Black soldiers were shot down by some of their captors.4
The saddest affair
The Park Service's battle summary estimates 5,289 casualties, 3,798 Union and 1,491 Confederate; the Petersburg park's own account speaks of nearly 5,500. Ferrero's division was badly mauled.5
Nothing had changed on the map. The Park Service suggests the Crater may have been Grant's best chance to end the siege of Petersburg; instead both armies settled into eight more months of trench warfare. Burnside was relieved of command for his part in the failure, Mahone was promoted to major general, and Grant called it the saddest affair he had witnessed in the war. The longer story of the campaign is in our article on the siege of Petersburg.6
