Also called the "Battle of Old Men and Young Boys", it was fought on June 9, 1864 just outside Petersburg. The armies of Lee and Grant were deadlocked just outside of Richmond in their Cold Harbor defenses. Butler knew Grant would probably soon attack Petersburg since it was the key supply point for Richmond. By way of intelligence from slaves and Confederate deserters and a captured Confederate map, Butler realized Petersburg was not well defended. In Petersburg, Confederate generals Beauregard and Wise had only 2,200 militiamen guarding the city. One Petersburg citizen called them a collection of "greyhaired men, and beardless boys." Some were not even equipped with rifles. Butler saw an opportunity and sent a force of 3,400 infantrymen along with 1,300 cavalry to attack Petersburg before Grant could get there. The Union infantry attacked from the east while the cavalry attacked from the south using the Jerusalem Plank Road. The infantry attack was intended as a diversion while the cavalry entered the city from the south. But the 2,500 Confederate defenders fought off both attacks. The infantry was stopped by the Dimmock Line which had been constructed to stop any such attacks. After the attacks failed, Butler withdrew.
Meade’s Army of the Potomac marched from Cold Harbor to support Butler. Meade's leading XVIII Corps crossed the Appomattox River and attacked Petersburg on June 15. The Confederate defenders were driven back to Harrison Creek. The Union XVIII Corps was then relieved by the II Corps. The next day, June 16, II Corps captured another part of the Confederate line. Beauregard moved more defenders to hold the Union troops while Lee, now aware of the situation at Petersburg, rushed troops to the city. On June 18, the Union II, XI, and V Corps attacked but were beaten back with heavy casualties. Now the Confederate fortifications were heavily defended and all hopes of an easy Union victory were lost. This was the beginning of the siege of Petersburg. Rather than a tactical siege with short term goals, it now became a strategic siege involving a number of battles.
Continuing their attacks, the Union Army under Grant began their third offensive against Richmond-Petersburg. General Winfield Scott Hancock's II Corps and two divisions of General Philip Sheridans cavalry crossed the James River at the "Deep Bottom" oxbow. They crossed at night to threaten Richmond. The plan called for the infantry to push the Confederates to the west. Then the cavalry could attack the railroad that connected Lee to the Confederate army under General Jubal Early still in the Shenendoah Valley. Sheridan's cavalry was then to attack Richmond if possible. But after breaking through the Confederate line, the Union offensive stalled. The Union cavalry was counterattacked by Richard H. Anderson's Confederate infantry. But the counterattack was defeated by the dismounted cavalry with their Spencer repeating carbines. But late on July 28, Hancock and Sherman withdrew back to Deep Bottom. The next night, July 29/30, they crossed the James River back to their own lines. They left a garrison to guard the crossing at Deep Bottom. Both sides could claim a victory. The Union forces defeated the Confederate infantry at Darby farm. But the withdrawal afterwards allowed the Confederates a victory. It was a Union victory strategically because their attack on the Virginia Peninsula caused Lee to move five and a half divisions north of James River. This weakened Petersburg leaving only four Confederate divisions to fight there. While Hancock and Sheridan were diverting Lee's attention, a mining operation was going on at Petersburg. A long tunnel was being dug by a regiment of Pennsylvania coal miners. It was dug right up to a Confederate strongpoint.
At this point in the siege, Lee's army had strengthened the Petersburg line. They dug breastworks out of rifle pits. At night, with pick and shovel, they then turned the breastworks into deep trenches. Pointed stakes turned outwards were designed to break up any frontal attacks. The area between the two lines became a no man's land. The summer that year was hot and dry. Streams and springs were quickly drying up causing a water shortage on both sides. The siege was quickly becoming a stalemate.
At a part of the Union line that was only from the Confederate line, the 48th Pennsylvania regiment was dug in. They were below the top of a ridge and part of their lines could not be seen by Confederates, blocked by the terrain. The 48th Pennsylvania regiment was made up of anthracite coal miners. Their commander heard his men remark, "We could blow that damned fort out of existence if we could run a mine shaft under it!" He passed the idea up to Burnside who agreed to the idea and digging started on June 25. Confederates on the ridge began to hear the sounds of picks and shovels under them. They dug several listening shafts. But when the digging sounds stopped on 23 July, they quit looking and dismissed any danger from mining. By the afternoon of July 28 the explosives were ready. Burnside's Fourth Division, including nine regiments of African American troops were trained to bypass the crater the explosion would cause and attack immediately after the explosion. These were fresh troops and their morale was high. At the last minute, Burnside's plan was changed by his commander General Meade to send in white troops. Meade said he did not want to be responsible for the "massacre" of colored troops.
Just before 5:00 am the explosion blew up a Confederate artillery battery and most of an infantry regiment. The blast killed at least 278 Confederates instantly. The crater caused by the explosion was more than long, across and deep. Following the explosion, the untrained Union troops were slow to leave their trenches. Instead of avoiding the crater they ran right into it. The walls of the crater exposed red clay making them too slippery to climb out of. The Confederates recovered quickly and began firing down directly on the Union troops who were unprotected. To try to save the situation, after four hours of fighting Burnside ordered the black troops to attack. At this point they could only follow the white soldiers into the crater. They had to force their way past the dead, wounded and demoralized white troops to get into the fight. As more Confederates joined in, they set up a tremendous crossfire into the crater. Mortar shells were dropped on the Union troops and the Confederate cannons were rolled up to the edge and fired canister shot at the soldiers trapped in the crater. The situation quickly turned from a one-sided battle into a race riot. As Union soldiers surrendered, black soldiers were given no quarter. Those who were allowed to surrender were murdered by Confederate troops as they were marched to the rear. Some Confederates later expressed regret that they could not kill them fast enough, as a few black troops made it to the rear alive.
The fighting went on for eight and a half hours. Burnside's IX Corps suffered 3,800 casualties. Lee's army lost about 1,500 who were killed, wounded or missing. But the black troops lost 1,327 men, 450 of whom surrendered. Most of these were murdered by Confederate soldiers as they were marched to the rear under guard. The failure and horror over what happened at the Battle of the Crater caused Burnside to be relieved of his command. He was placed on indefinite leave of absence with no orders to return to duty. This effectively ended his army career. He resigned from the army less than nine months later, on April 15, 1865.
General Grant was using a strategy of simultaneous operations on both sides of the James River during the summer of 1864. Grant was forcing Lee to use Confederate troops on two fronts. Lee, on the other hand, had General Early in the Shenandoah Valley. While Grant and Lee were engaged at Petersburg, Early launched an offensive into the North that was threatening Washington, D.C..