Battle of the Crater

July 30, 1864:

After Lee held at bay Grant's attempt to seize Petersburg on June 15, the battle settled into a stalemate. Grant had learned a hard lesson at Cold Harbor about attacking Lee in a fortified position and was chafing at the inactivity to which Lee's trenches and forts had confined him. Finally, Lt. Col. Henry Pleasants, commanding the 48th Pennsylvania Infantry of Maj. Gen. Ambrose E. Burnside's IX Corps, offered a novel proposal to break the impasse.
Pleasants, a mining engineer from Pennsylvania in civilian life, proposed digging a long mine shaft underneath the Confederate lines and planting explosive charges directly underneath a fort (Elliott's Salient) in the middle of the Confederate First Corps line. If successful, this would not only kill all the defenders in the area, it would also open a hole in the Confederate defenses. If enough Union troops filled the breach quickly enough and drove into the Confederate rear area, the Confederates would not be able to muster enough force to drive them out, and Petersburg might fall. Burnside, whose reputation had suffered from his 1862 defeat at the Battle of Fredericksburg and his poor performance earlier that year at the Battle of Spotsylvania Court House, gave Pleasants the go-ahead.
Digging began in late June, but even Grant and Meade saw the operation as, "A mere way to keep the men occupied," and doubted it of any actual strategic value. They quickly lost interest and Pleasants soon found himself with few materials for his project, to the extent that his men had to forage for wood to support the structure. Work progressed steadily, however. Earth was removed by hand and packed into improvised sledges made from cracker boxes fitted with handles, and the floor, wall, and ceiling of the mine were shored up with timbers from an abandoned wood mill and even from tearing down an old bridge. The shaft was elevated as it moved toward the Confederate lines to make sure moisture did not clog up the mine, and fresh air was pumped in via an ingenious air-exchange mechanism near the entrance; the miners kept a fire continually burning at the bottom of a single ventilation shaft located behind Union lines, near the entrance of the mine but behind a bulkhead isolating it from the outside air. Meanwhile, a wooden duct ran the entire length of the tunnel. The fire heated stale air, forcing it up the ventilation shaft and out of the mine. The resulting vacuum then sucked fresh air in from the mine entrance, and carried it through the wooden duct to the location where the miners were working. This precluded the need for additional ventilation shafts that could have been observed by the enemy, and served well in disguising the diggers' progress. On July 17, the main shaft reached under the Confederate position. Rumors of a mine construction soon reached the Confederates, but Lee refused to believe or act upon it for two weeks before commencing countermining attempts, which were sluggish and uncoordinated, and were unable to discover the mine. General John Pegram, whose batteries would be above the explosion, did, however, take the threat seriously enough to build a new line of trenches and artillery points behind his position as a precaution.

The mine was in a "T" shape. The approach shaft was 511 feet (156 m) long, starting in a sunken area downhill and more than 50 feet (15 m) below the Confederate battery, making detection difficult. The tunnel entrance was narrow, about 3 feet (1 m) wide and 4.5 feet (1.4 m) high. At its end, a perpendicular gallery of 75 feet (23 m) extended in both directions. Grant and Meade suddenly decided to use the mine three days after it was complete after a failed attack known later as the First Battle of Deep Bottom. The Federals filled the mine with 320 kegs of gunpowder, totaling 8,000 pounds (3,600 kg). The explosives were approximately 20 feet (6 m) underneath the Confederate works and the T gap was packed shut with 11 feet (3 m) of earth in the side galleries and a further 32 feet (10 m) of packed earth in the main gallery to prevent the explosion blasting out the mouth of the mine. On July 28, the powder charges were armed.
The plan called for the mine to be detonated between 3:30 and 3:45am on the morning of July 30. Pleasants lit the fuse accordingly, but as with the rest of the mine's provisions, they had been given poor quality fuse, which his men had had to splice themselves. After more and more time passed and no explosion occurred (the impending dawn creating a threat to the men at the staging points, who were in view of the Confederate lines), two volunteers from the 48th Regiment (Lt. Jacob Douty and Sgt. Harry Reese) crawled into the tunnel. After discovering the fuse had burned out at a splice, they spliced on a length of new fuse and relit it. Finally, at 4:44 a.m., the charges exploded in a massive shower of earth, men, and guns. A crater (still visible today) was created, 170 feet (52 m) long, 100 to 120 feet (30 to 37 m) wide, and at least 30 feet (9 m) deep.
The explosion immediately killed 278 Confederate soldiers, and stunned Confederate troops did not direct any significant musket or artillery fire at the enemy for at least 15 minutes. However, Ledlie's untrained division was not prepared for the explosion, and reports indicate they waited ten minutes before leaving their own entrenchments. Footbridges were supposed to have been placed to allow them to quickly cross their own trenches, but these were missing, meaning the men had to climb in and out of their own trenches just to reach no-man's land. Once they had wandered to the crater, instead of moving around it as the black troops had been trained to do, they thought it would make an excellent rifle pit and it would be well to take cover. Therefore, they moved down into the crater itself, wasting valuable time while the Confederates, under Brig. Gen. William Mahone, gathered as many troops together as they could for a counterattack. In about an hour's time, they had formed up around the crater and began firing rifles and artillery down into it, in what Mahone later described as a "turkey shoot". The plan had failed, but Burnside, instead of cutting his losses, sent in Ferrero's men. Now faced with considerable flanking fire, they also went down into the crater, and for the next few hours, Mahone's soldiers, along with those of Maj. Gen. Bushrod Johnson and artillery, slaughtered the IX Corps as it attempted to escape from the crater. Some Union troops eventually advanced and flanked to the right beyond the Crater to the earthworks and assaulted the Confederate lines, driving the Confederates back for several hours in hand-to-hand combat. Mahone's Confederates conducted a sweep out of a sunken gully area about 200 yards (180 m) from the right side of the Union advance. This charge reclaimed the earthworks and drove the Union force back towards the east.
In later stages of the battle, many Union casualties were black soldiers killed by Confederate bayonets and musket fire even after surrendering – a direct violation of the rules of war prevalent at the time (the Lieber Code). At the same time, black soldiers were also bayoneted by white Union soldiers who feared reprisal from victorious CSA troops.  Union casualties were 3,798 (504 killed, 1,881 wounded, 1,413 missing or captured), Confederate 1,491 (361 killed, 727 wounded, 403 missing or captured). Many of the Union losses were suffered by Ferrero's division of the USCT.

The whole concept of the mine and explosion are so hard to fathom.  The engineering which went into this was just amazing.  When I first read the account of the battle, I couldn't believe I had never heard of it before.  The battle itself was a disaster, but the mine tunnels were massive achievements.  The story should be taught to all high school students when they cover the Civil War in American History class.