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The use of military earthworks in the Civil War was on an unprecedented scale. Earthworks can be defined generally as any structure made of dirt for military purposes. Soldiers in the Civil War built earthworks for the same reasons Roman armies did: to protect an important place, to help a small number of defenders resist a larger number of attackers, or to surround and cutoff a place important to the enemy. Their forms and complexity evolved in response to improvements in weapons technology.

When the United States Military Academy was established at West Point in 1802, it was modeled after French military academies. Civil and military engineering were the cornerstones of the curriculum. Dennis Hart Mahan, who taught at West Point for 47 years, first published his Complete Treatise on Field Fortification, with the General Outlines of the Principles Regulating the Arrangement, the Attack, and the Defense of Permanent Works in 1836. In it he summarized current European theories of field fortification.

Many of these theories could be traced back to principles that were developed by military engineers in the 17th and 18th centuries in response to the introduction of gunpowder and moveable artillery. First, any fortification was only as strong as its weakest part. Each fortification should be built within range of adjacent fortifications so that they could provide mutual support. Cannoneers and infantrymen instinctively fire straight ahead, so every fortification had to have at least one section that faced each expected direction of attack. Each section was responsible only for the area immediately in front of it. There should be as little dead ground as possible, that is, areas that could not be fired on by guns inside the fortification. Earthworks were better at absorbing the impact of bullets and cannon balls than fortifications of stone or brick. Topography, above all else, drove design. Each fortification had to be uniquely designed for the particular piece of ground it occupied.

In the late 17th century, Louis XIV's chief military engineer, Sebastien de Vauban, developed a "scientific" method to use earthworks offensively. Men besieging a fortified position first constructed lines of earthworks facing the fortification, but beyond the range of its guns. During the night, they dug a zigzag trench leading towards the target and built another line at the new position. Once they got close enough, they hauled artillery forward to the protected position and bombarded the walls at close range, eventually opening the way for an infantry charge. Vauban often added an outer ring of interconnected and mutually supporting earthworks. These detached outer works were often used to protect storage depots, supply lines, and artillery batteries, and to slow the enemy's approach. It did not take many soldiers or cannons to man these earthworks, which could be quickly thrown up and as quickly abandoned.

Most earthworks were built before the battle began, but armies also erected entrenchments on the battlefield, primarily to protect artillery. At first, infantrymen relied on sunken roads, walled farmhouses, and other "found" defenses to protect themselves. By the early 19th century, some officers were ordering their men to dig in. Even a shallow parapet could deflect a bounding cannon ball up and over the heads of the soldiers lying behind it.

In the mid 19th century, weapons technology changed again, as European and American armies began to rely on mass-produced rifled weapons. Cutting spiral grooves into the inside of the barrels of cannon and muskets made them more powerful and more accurate at longer ranges. Rifle-muskets fired what the soldiers called a "minie ball," named after its innovator, Claude Etienne Minié. An experienced soldier could load and fire a rifle-musket as quickly as a smoothbore musket, and he could kill a man at 300 yards, three times the distance of the old smoothbores.

Rifle-muskets made warfare a much more dangerous business for infantrymen. Facing smoothbore muskets, an attacking army could approach within a hundred yards of a line of defenders without incurring serious losses and then make a last dash with bayonets. Attackers facing men armed with rifle-muskets could rarely cross that last hundred yards without losing so many men that they could no longer manage a decisive bayonet charge.

When the Civil War began, more than half of the Confederate and Federal units were armed with smoothbore muskets, but both sides soon equipped their front-line troops with rifle-muskets. Military theorists were still debating the lessons of rifled firepower and entrenchment, but Mahan's view was clear. In the introduction to his 1861 edition, he wrote: "The great destruction of life in open assaults . . . must give additional value to entrenched fields of battle."¹ Nearly every West Point graduate who served in the Civil War on either side learned his fortification theory and methods from Mahan.

By 1864, all troops were regularly entrenching on the battlefield, as the spade replaced the bayonet. For the common soldier, entrenching was a rational response to the increasing deadliness of the battlefield--digging increased both his effectiveness and his odds of survival. European countries sent observers to the United States while the war was still going on to study the use of earthworks in places like Richmond, VA and Petersburg, VA. What they learned here, they used in World War I, where trenches defined that bloody conflict.

Questions for Reading 3

1. What were earthworks supposed to accomplish?

2. What principles of fortification did Civil War officers learn at West Point? How were they applied at the Siege of Corinth? at the Battle of Corinth?

3. How did the Siege of Corinth resemble Vauban's technique for attacking fortifications? How did it differ?

4. What change in offensive weapons occurred about the time of the Civil War?

5. A popular view held that:

At the beginning of the Civil War, the opinion in the North and South was adverse to the use of fieldworks, for the manual labor required to throw them up was thought to detract from the dignity of a soldier. . . . The epithet of dirt-diggers was applied to the advocates of entrenchments. Expressions were heard to the effect that the difference ought to be settled by a fair, stand-up fight in the open.²

Reading 3 was excerpted from David Lowe and Paul Hawke, "Military Earthworks-Historical Overview," typescript draft prepared for "Guide to Sustainable Earthworks Management," National Park Service, in association with the Georgia Trust for Historic Preservation.

¹Dennis Hart Mahan, A Treatise on Field Fortification (New York: John Wiley, 1851), v.
²Capt. E. O. Hunt, "Entrenchments and Fortifications," in Photographic History of the Civil War, Francis Trevelyan Miller, ed. (New York: T. Yoseloff, 1957), vol. 5, 194-218.