Field Armies and Fortifications in the Civil War The Eastern Campaigns, 1861-1864
By Earl J. Hess
The University of North Carolina Press Copyright © 2005 The University of North Carolina Press
All right reserved. ISBN: 0-8078-2931-5
Chapter One Engineering War
Responsibility for fortifications in the pre-Civil War army rested with the Corps of Engineers, the elite of the military establishment. Created initially by the Second Continental Congress in 1779 and renewed in different form by the Congress of the new government in 1794, the corps was institutionalized in its current form in 1802. A separate group of topographical engineers, responsible for mapmaking, was created in the War of 1812 and given its own institutional status in 1838 as the Corps of Topographical Engineers. The U.S. Engineer Department was created immediately after the War of 1812 to serve the administrative needs of the corps. It was headed by the chief engineer.
The Corps of Engineers owed its status to its role as keeper of a body of technical knowledge and its tight connection with the U.S. Military Academy at West Point. Created in 1802, the academy had a curriculum that was heavily oriented toward engineering. Political support for it stemmed largely from the assumption that West Point could produce a number of well-trained engineers who would eventually return to civilian life with their technical skills. The Corps of Engineers controlled the academy. Only engineer officers were appointed as superintendents, and most of the faculty were former or current members of the corps. Beginning in 1842, the assistant professor of engineering was required to participate in postgraduate training in military engineering under the academy's most famous faculty member, Dennis Hart Mahan, the acknowledged expert on fortifications in the United States. Mahan put his students through a rigorous pace in this course, requiring each one to design a fortification for a particular site and plan an attack against it.
Cadets also were exposed to practical experience in field fortification. In his third year at the academy, Cyrus B. Comstock took a course called Practical Engineering. He and his classmates spent two hours every day making fascines, gabions, and sap rollers. The class regularly visited Washington Valley, where the only company of engineers in the army maintained a demonstration site. Here the cadets watched as saps and parallels were made, inspected "a small lunette with palisaded gorge," or looked at the effects of 10-inch Columbiad fire on "different materials for embrasures." They used sticks to profile the shape of a parapet and studied examples of several different types of obstructions, from abatis to chevaux-de-frise. Civil engineering was a large component of the academy curriculum as well. The top graduates of the academy, roughly 12 percent, were commissioned directly into the engineers, the topographical engineers, or as ordnance officers.
The prestige of the Corps of Engineers, as well as its connection to the academy, was the basis of its elevated status within the army, a status jealously guarded by the officers who headed the corps. The corps liked to throw its weight around during intramural conflicts, and it also was the most politically active branch of the army. Corps heads often fought with politicians over West Point and the other major aspect of the corps' existence, its responsibility for building and maintaining an ambitious and very expensive system of coastal forts. Approved in the wake of the army's dismal performance in the War of 1812, the Third System consisted of about twenty-five masonry forts of various sizes and designs strung out along the coastline of the United States. Costing millions of dollars and mostly complete by the time of the Civil War, it was "the centerpiece of national defense," in the words of historian William B. Skelton.
The emphasis on coastal forts helped to justify the maintenance of the Coast Survey, created in 1807 to map the long coastline of the country. It operated under a limited budget and relied heavily on navy and army engineers for survey duties. The Coast Survey also hired promising civilians and gave them valuable topographical engineering experience. It provided another pipeline, besides West Point, for the training of engineers experienced in government-sponsored projects.
As the primary repository of technical expertise in engineering, the corps had a heavy influence on the many U.S. military missions sent to observe European armies. American officers traveled to Europe more than 150 times from the end of the War of 1812 until the outbreak of the Civil War. While more than half of those trips were undertaken as private travel by officers on leave, the rest were officially financed observer missions. The Thayer-McRee Mission of 1815-17 was important in bringing to America the idea that all things French were the final word in military affairs.
But more important than the Thayer-McRee Mission was the Delafield Commission of 1855-56. Three officers took part: Maj. Richard Delafield of the engineers, Maj. Alfred Mordecai of the Ordnance Department, and Capt. George B. McClellan of the cavalry. All three had originally been commissioned into the Corps of Engineers upon their graduation from West Point. The object of the commission was to observe military operations in the Crimean War, but the three officers traveled all over Europe, observing the gamut of military matters. They left on April 11, 1855, and visited England, France, Prussia, Poland, Russia, Berlin, Vienna, and Constantinople. Diplomatic red tape and military suspicions on the part of the French delayed their arrival at the theater of war until the siege of Sebastopol was over. The Americans reached Sebastopol a month after the city fell to the combined French and English armies on September 8, 1855. After a month of observation, they returned to Vienna and then toured Italy, the Rhine Valley, Waterloo, Paris, and London. By the time the three officers returned to New York on April 28, 1856, they had traveled 20,000 miles.
The Delafield Commission was unique in that it was the first to survey several countries and the first to see the immediate aftermath of operations. Each commissioner wrote a separate, lengthy report. Delafield concentrated on engineering but did not complete his report until November 1860. Mordecai wrote on artillery and ordnance, while McClellan wrote on cavalry, to a degree, but mostly ranged widely across the whole spectrum of military matters.
The result of their labor was impressive; each man wrote with a fine degree of professionalism, detail, and evaluation. But none of them discerned very well how the early signs of technological innovation were beginning to change military operations. They noted a wide array of new developments, ranging from the use of processed foods and submarine torpedoes to the construction of a military railroad for the tactical support of the English army. But they failed to ponder the effect of the widespread use of rifles on tactical formations. The technological developments were eagerly described, often in minute detail, but there was no recognition that they might begin to challenge how armies traditionally fought.
Overall, the commissioners took away from their long tour of Europe an awareness that the scale of warfare had changed and that the mobilization of manpower and military resources had increased to create expanded field armies. But they also sensed a threat to American security from this and argued the need for strengthening the Third System of seacoast fortifications.
It was a rather self-serving performance, however, and much of it reinforced old ways of doing things in the American military, despite some minor technical recommendations. Also, the commissioners unsuccessfully tried to portray the French model as outdated and the Russians as the truly admirable belligerent in this conflict. Objectively, the Russian nation and its army were hardly suitable models for intelligent professionals of a modernizing nation; the suggestion fell on deaf ears.
Delafield's comments on matters relating to fortifications were interesting. He focused intently on seacoast forts everywhere he went and provided extraordinary maps, sketches, and diagrams of dozens of works in several countries. Delafield also was impressed by the European art of protecting fixed assets on land with scientifically designed permanent fortifications. He emphasized the success of the huge masonry forts built by the Russians to protect the entrance to the harbor at Sebastopol in repelling an Allied naval attack in October 1854.
But Delafield paid some attention to field fortifications as well. Both he and McClellan lauded the Russians for the tenacity with which they defended a line of hastily constructed fieldworks to cover the southern approaches to Sebastopol. The Russians held out for eleven months, even though they were heavily outnumbered in both infantry and artillery in the latter stages of the siege. "Such was the efficacy and power of temporary field fortifications, with inexhaustible supplies of the munitions of war," commented Delafield. The Russians were the first to use what came to be called rifle pits, small holes dug for one to twenty men forward of their defense line. Soldiers armed with rifles harassed Allied work parties on a daily basis from these pits, which were typically protected by gabions filled with stone or dirt. Delafield felt this tactic of harassment was "unusual." He also gathered a number of photographs of the Russian works at Sebastopol and included exquisite line drawings based on them to illustrate his report. Few other visual documents convey the squalor of a small fortification that has endured months of bombardment better than these remarkable illustrations.
All three reports of the Delafield Commission were widely distributed in the army and were well respected by officers and interested civilians alike. But these reports had limited impact on the thinking and doctrine of the American army. This was due in part to the onset of the Civil War soon after the reports were published, and to the fact that there were relatively few recommendations in the reports. Delafield's comments on the efficacy of field fortifications apparently had no influence on professional army officers, and the fact that the coming Civil War would be fought by an avalanche of volunteers who had never read the report made it even less influential. The significance of the Delafield Commission lies in the fact that the American army was obviously growing in its sense of professionalism and study. It still had a long way to go in terms of divining new trends that might affect how armies operated in the field and then moving aggressively toward meeting the challenges that change offered. McClellan sounded a plaintive note of despair in his report, which illustrated how far the army had to go to be a top-notch military force. He bemoaned the size of the American engineer establishment, calling it "ridiculously and shamefully small."
Theory and Doctrine
To the extent that the pre-Civil War army had a set of theories that could be called a doctrine, prevailing thoughts on the role of fortifications in the operations of field armies centered on whether they should be used for offensive or defensive purposes. Dennis Hart Mahan was the only influential American theorist in this regard. A graduate of the West Point class of 1824, Mahan studied at the French School of Application for Artillery and Engineering at Metz from 1825 to 1830. He returned to West Point soon after he came home to teach engineering, and he held the position until his death in 1871. Mahan had an extraordinary influence on the creation of professional standards of military engineering in the United States, both through his classes at West Point and through his book A Complete Treatise on Field Fortifications (1836). He later wrote six more books on warfare and engineering. Mahan also was primarily responsible for establishing standards of professionalism in civil engineering. The several reprintings of his Complete Treatise not only informed regular officers, but they were widely read by the pre-Civil War militia and by volunteer officers during the war.
Mahan revised prevailing French military thinking about the role of fortifications in field operations. Theorists of Napoleon's day had advocated maneuver and flanking, the indirect approach, to win battles quickly and decisively. This was largely rejected following Napoleon's defeat. Instead, theorists such as Antoine Henri Jomini favored the direct approach, or massing troops for frontal attacks. Napoleon himself had adopted such tactics on occasion during the later years of his career, most notably at the battle of Borodino during the invasion of Russia in 1812. Jomini and others even believed the spirited offensive could be successful against field fortifications. These post-Napoleonic writers were most influential until about 1840, during the period when Mahan was studying in France, and most American commentators adopted Jomini and his compatriots with enthusiasm.
One of these French theorists, Francis Gay de Vernon, a professor of fortification and the art of war at the Ecole Polytechnique also urged the use of field fortifications to protect the army. Vernon argued that fieldworks should even be used to facilitate offensive action, as long as they were designed so the attacking force had an opening in the works to debouch and mass in the open for the assault. Vernon's book on war and fortification was used at West Point from 1817 through 1830.
Mahan was dedicated to the direct approach, but he significantly revised how it should be conducted. He argued that the poorly trained volunteer force that the United States relied on to fight its wars could not conduct successful attacks on fortified positions unless the defending army was somehow damaged first. Even if U.S. volunteer troops were successful in attacking a well-fortified position defended by a fresh army, the losses would be prohibitive. Mahan believed the volunteers were more valuable to the country as permanent civilians than as temporary soldiers. Moreover, the small regular army was too valuable to waste in frontal attacks on strong positions.
Mahan instead advocated what he called an "active defense." First, use field fortifications to create a defensive position, entice the enemy to attack it, and damage him significantly. Then, follow up with a counterattack that would be sure to take the enemy position and scatter or decimate the opposing army. This was a smart adaptation of prevailing French theory to the peculiar conditions of the American military force. Whether it was practical in the field was another issue. The enemy would have to cooperate in developing such a scenario, and volunteers, who often were naively enthusiastic about attacking with little preparation, would have to be convinced of the need to dig in before the first shot was fired.
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