Civil War Field Fortifications: Permanent Fortifications

Civil War Field Fortifications

IV. Permanent Fortifications

Although a complete and thorough treatment of permanent fortifications is well beyond the scope and competence of this website some basic information on how they were both different and similar to field fortifications seems appropriate for a more complete understanding of field fortifications. Permanent fortifications were distinguished from field fortifications primarily by the durability of the materials used in their construction, their greater size, and stronger profile. Where a decent field work could be constructed over the course of a few days, permanent fortifications required years, sometimes decades, of steady labor to complete. Fort Morgan which guarded the main ship channel into Mobile Bay, Alabama was started in 1819, but not completed until 1834. As with field fortifications, permanent fortifications were designed to increase their garrison's defensive endurance, but unlike field fortifications, permanent fortifications were constructed to guard strategically significant points for indefinite periods of time.

The basic elements of field and permanent fortifications were essentially very similar, but there were some important differences besides the obvious size differential. In theory permanent works consisted of a raised mound that enclosed the interior of the fortified space, called a rampart, that also raised the work's parapet and terre-plein to a commanding height above the ground immediately surrounding the fort. A wide ditch combined with tall masonry revetted scarp and counterscarp walls formed an almost insurmountable obstacle to attempts to seize the fortification by escalade and storming. A covered way around the top of the counterscarp wall provided a defensive position where infantry and light artillery could oppose an attacking enemy force while the glacis, which sloped outward from the covered way, both provided clear fields of fire and protected the scarp wall from distant artillery fire. As with field fortifications these basic elements could be modified to both suit the fortification requirements of particular sites and the defensive objective of the fortification. Ramparts and covered ways were not integral elements of the profile of field fortifications and glacis were something of a luxury that the limits of time and labor did not permit.

Overlapping columns of fire were just as important to a good defense of permanent fortifications as they were to field fortifications. The best and most economical means to establish a reciprocal defense was to enclose the fortified space with a series of bastions and curtains. Bastions were lunette shaped works consisting of two faces and two flanks positioned at the salient angles of the scarp wall. Curtains were straight sections of scarp wall that connected two bastions. This system produced a strong network of overlapping columns of fire that would catch an attacking force attempting to approach the scarp wall with direct, slanting, and enfilade fire. The area covered by fire from a fort's main artillery armament could be substantially increased when the guns were mounted en barbette along the parapet.

The strength of permanent fortifications imparted a certain finality to their defense that field fortifications lacked. If the parapet of a field work was breached, the damage could be repaired quite quickly by a few men armed with shovels. When the scarp wall of a permanent fortification was breached, it stayed breached, even if it could be barricaded or covered by a hastily constructed retrenchment the weakness and exposure to assault persisted. Thus the very durability of materials used to construct permanent fortifications combined with the massiveness of the structure itself imposed a degree of brittleness that could be made to work against a successful defense by a resourceful attacking force that reached the crest of the counterscarp quickly. The scarp wall could be covered by outworks that both protected it from distant fire and compelled an attacking force to overcome a series of defensive barriers before it could begin operations to breach the scarp wall. By delaying an attacking force beyond range of the scarp wall outworks also prolonged the defense which improved the garrison's chances of receiving aid from an army of relief while wearing down the attacking army's will to fight its way to a successful conclusion to its siege operations.

Sea Coast Fortifications

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