Digging Down and Blowing Up: Mines

^{Marine Corps photo from National Archives}

^{Blowing up enemy fortifications is still being done. Here marines use a demolition charge to destroy a Japanese cave on Okinawa.}

U.S. Grant’s Union armies were closing in on Richmond, capital of the Confederacy in 1864. Robert E. Lee’s men dug an elaborate system of trenches, bunkers, and strong points north of the city, so Grant tried to attack from the south while he held the Confederates in place north of Richmond. But Lee had begun fortifying the southern approach, around Petersburg, before the Yankee move. The Confederate fortifications were immensely strong around Petersburg. At one point, the troops of General Ambrose Burnside’s Ninth Corps were only 150 yards from an enemy salient protected by a mass of trenches and dugouts on a hill top. Confederate fire from the fort was so heavy there was no way to move forward.

“We could blow that damn fort out of existence if we could run a mine shaft under it,” said a soldier of the Forty‑Eighth Pennsylvania Infantry. The forty‑eighth, recruited in the anthracite district of Pennsylvania, was full of coal miners. Colonel Henry Pleasants, the regimental commander, overheard the soldier’s comment. Pleasants himself was a mining engineer in civilian life. He asked the army engineers about mining the fort. Mining enemy fortifications is an ancient tactic, one that was practiced long before explosives were discovered. The pre‑explosive method was to tunnel under a fort’s walls, propping them up with timber as you dug. When the mine was completed, the besieger set fire to the timber, and the wall collapsed. But when Pleasants consulted the army engineers, they said the project was impossible. The tunnel would have to be 500 feet long – too long to allow for ventilation.

Pleasants was not discouraged. He convinced his superiors, right up to General George G. Meade, commander of the Army of the Potomac, that the project was feasible. Meade convinced Grant, the commander‑in‑chief. Grant gave Burnside’s Ninth Corps the job of blowing up the fort and opening the way to Petersburg. Burnside was delighted. Breaching the rebel line would make up for his bloody failure in the attack on Fredericksburg in 1862. He began training his only fresh troops, the eight African American regiments of the Fourth Division. When the mine went off, he expected that it would kill most of the enemy soldiers in the fort and stupify the survivors in the nearby trenches. The assault force was to run around the crater caused by the explosion and continue straight on into Petersburg. The troops following them would widen the breach, prevent the Confederates from closing it by blocking reserves, and follow the Fourth Division into the rebel city.

Meanwhile, Pleasants’s miners were tunneling toward the Confederate fort.

They got no help from the official engineers, so they improvised their own tools and scrounged up lumber to reinforce the shaft. Pleasants, using a borrowed the odolite (an instrument for measuring vertical and usually also horizontal angles), plotted the shaft and designed a ventilation system using a fire to create a draft and suck fresh air through the 511‑foot tunnel. When they reached a point they calculated was under the Confederate position, the miners dug lateral shafts and filled them with 8,000 pounds of gunpowder.

The stage was set for an explosion that would be heard around the world.

Then at almost the last minute, Meade changed the plan. He decided that Burnside’s black troops were not up to leading the assault. Instead of the black division, the assault would be spearheaded by the division led by James H. Ledlie, a general with a mediocre combat record and serious drinking problem.

Ledlie’s troops had not been trained this unusual type of assault. The black Fourth Division would be the last of Burnside’s men to enter the breach.

The mine exploded with a deafening blast. The Confederate strongpoint was replaced by a hole 170 feet long, 60 feet wide and 30 feet deep. A battery of Confederate artillery and a whole infantry regiment were either blown into the air or buried under tons of dirt. Ledlie’s untrained riflemen dashed towards the crater while their commander stayed in his headquarters swilling rum. When the Union soldiers got to the crater, they stopped and stared, dumbfounded by the destruction. Some even ran down into the hole; Climbing out of it was not easy, they found. The other divisions, equally untrained, joined Ledlie’s in mill‑ing around – and inside – the crater. The black division, the only one trained to exploit the explosion, had trouble getting through the mob of white colleagues.

By that time, the Confederates had had time to gather their reserves and counterattack. The Union attack was a failure, and the Federal troops were driven back with heavy casualties.

Mining, which had been so devastating against ancient, medieval, and early modern stone forts, has not had nearly as much success against modern earthworks. It was tried again in World War I, opening the Battle of the Somme (see Chapter 27). In preparation for the attack on the German lines, British engineers had mined a German strongpoint called the Hawthorn Redoubt and placed 18 tons of high explosive under it. At 7:20 a.m., 10 minutes before the attack, they touched off the explosives. The blast practically leveled the hill and killed all the Germans manning the redoubt. It did not, however, affect the machine guns in the adjoining German positions. The infantry assault was a total failure. Few of the Tommies even reached the German lines, and the British lost 20,000 dead on that first day of the battle. Mining would have been more successful in the smoothbore era, when the range of small arms was less than 1/10 of that of rifled guns.

The origin of mines is lost in the mists of prehistory. There were two principal defenses against mines in those days. One, known to all fanciers of medieval castles, was the wet moat. At the time primitive mines were being used, there was no way to dig under a body of water while preventing the water from pouring down from the moat through the earth and filling the tunnel, if it didn’t collapse the tunnel outright.

The second defense was the countermine. To locate enemy mines, the defenders would listen intently, sometimes using inverted shields placed on the ground to amplify the noise. When the Turks were besieging Constantinople in 1553, Johann Grant, a German engineer helping to lead the defense, half‑buried a line of drums just behind the city walls. He put some dried peas on each drum.

Vibrations of the drum made the peas dance and showed Grant where the Turks were digging. Grant then had his own men mine the Turkish mines. Some, he blew up with gunpowder; others, he filled with poisonous sulfur dioxide generated by burning sulfur; still others, he flooded. If nothing else was available, Grant sent infantry through his tunnel to the enemy tunnel, where they killed the Turkish diggers and pulled down the reinforcements of their tunnel, causing the enemy mine to collapse.

During the Turkish siege of Rhodes, the defenders, the Knights of St. John, reached into the past for an anti‑mine weapon. They built a trebuchet (see Chapter 9) capable of shooting an enormous stone a short distance. The stone landed above the Turkish tunnel and collapsed it. The Knights also used countermines, as Suleiman the Magnificent recorded in his diary: “The miners meet the enemy, who uses a great quantity of flaming naphtha.” Pouring flaming naphtha from a countermine into a tunnel was an utterly devastating counterattack. The flames not only killed the miners, they burned the timber support of the tunnel, causing a cave‑in.

Strangely, gunpowder had been in use in cannons for some time before it occurred to soldiers to use it in mines. For years, the approved technique was the age‑old one of propping up the foundations of a wall with timber, and then burning the props. Even when gunpowder was first used, in the 15th century, historian Christopher Duffy says contemporary accounts indicate that it was merely used to help the underground fire burn more fiercely. The first use of gunpowder to blast down walls appears to have been in 1500, when Pedro Navarro captured a Turkish fortress on the island of Cephalonia.

The earliest mines were called mines because the same techniques were used that the men who burrowed into the earth in search of metals or other minerals used. When gunpowder was introduced, the military was again using a material that was also important in civilian mining, although the way it was used was quite different. Somehow, though, the military term “mine” came to be used for any quantity of explosives not used in guns, shells, or rockets that was used to harm an enemy, even if no tunneling was required. Explosive charges in the water, originally called “torpedoes,” became “mines.” Then, when explosives were placed on the surface of the ground or barely covered with earth, they were called “land mines,” as opposed to those intended to destroy shipping.