Modern Fortifications Summary

  • Last updated on November 11, 2022

The fortifications of the sixteenth century differ little from those of medieval and ancient times with regard to key features such as moats, towers, and walls.

Medieval FortificationsNature <index-term><primary>Fortifications;medieval</primary></index-term>and Use

The fortifications of the sixteenth century differ little from those of medieval and ancient times with regard to key features such as moats, towers, and walls. In the field of strategic use, as they had in the past, fortifications provided protection for key positions and served a strategic role as part of greater defensive lines. This role became more dominant in the twentieth century. However, such continuous lines of defense were not unknown before the modern period, as attested by the Great Wall of Great Wall of ChinaWallsChina, built in the third century b.c.e. and spanning almost 1,500 miles, and Hadrian’s Hadrian’s Wall[Hadrians Wall]Wall, built in the second century c.e. and extending more than 100 miles across Great Britain. The Romans also created hundreds of miles of less solid fortifications, known as the Limes (Roman defensive zones)Limes, to close off other parts of their empire. During the Middle Ages, continuous obstacles forming a defensive line were found from England to as far east as Russia.Fortifications;modernFortifications;modern

During the modern era, new forms of fortifications supplanted the castle and fortified cities in Europe. However, medieval-style fortifications remained in use in most of Asia, Africa, and the Americas. Thus, the major fortified sites of Japan, China, and the Indian subcontinent are more reminiscent of medieval cities than modern ones. Many fortifications in the Americas were also built in the more archaic style, with some notable exceptions, such as the sixteenth century Inca fortress of Sacsahuamán (Incan fortress)Sacsahuamán, overlooking Cuzco, and the easily defendable complexes of the Pueblo Indians of southwestern North America.


It has long been assumed that the cannon brought about the demise of the castle in Europe. However, this is not totally true. Although Castlescastles with weak, high walls did indeed succumb to the Cannons;and castles[castles]cannon, others continued in service for centuries. In the 1970’s a castle used by terrorists in Lebanon was able to resist the modern ordnance launched from Israeli jets. What did bring a major change to fortifications was the need to create positions that could more effectively mount cannons and resist cannon fire. Cannons mounted on high fortification walls proved less effective than those that were placed lower down, because they lacked “grazing fire,” or the field of fire in which a projectile is able to strike any object within its path above a certain height. As a result, the walls of many fortifications were lowered and made wider to accommodate large artillery pieces. At the same time, they became smaller targets by presenting a lower profile.

The first of these “improved” fortifications were built in western Europe. Italian Engineers;Italianengineers initiated some of the first significant changes in the 1480’s. The Sangallo Sangallo familyfamily of architects designed new forts in the Italian peninsula in the late fifteenth and the sixteenth century and in 1493 added bastions to Rome’s Castel Sant Sant Angelo castle (Rome)[santangelo]Angelo, originally built in 135-139 by the emperor Hadrian (76-138) as a mausoleum for himself and his successors. In the 1490’s a member of the Sangallo family built Sarzanello (fort)Sarzanello, a hilltop fort of triangular shape that included rounded bastions and a triangular Ravelinsravelin, or V-shaped outwork, to protect the entrance. The transition from medieval to Renaissance styles also appears in city Cities;fortificationsfortifications during the end of the fifteenth century in places such as Civita Civita CastellanaCastellana, north of Rome, and the Greek island of Rhodes, where bastions were added and the walls were modified.

At Salses, in modern-day southwestern France, a modernized fortification was built in 1498, improving on the Italian designs. Salses (fort)Salses proved too weak to resist French cannons at close range, however, and in 1503 it was redesigned with thicker walls, the height of which was already mostly concealed in a large ditch that protected them from direct artillery fire. The guns mounted atop the walls of the fort were close to ground level, allowing grazing fire.

At the end of the 1530’s, King Henry Henry VIIIHenry VIII (king of England)[Henry 08]VIII (1491-1547) of England, facing the threat of invasion from the European continent, protected his coastline with a series of new forts designed to mount artillery and muskets. These forts, located near the beaches, consisted of a series of rounded bastions surrounding a central circular keep and sitting in a deep and wide dry Moatsmoat. The best known of these forts are Deal (English fort)Walmer (English fort)Deal, Walmer, and St. St. Mawes (English fort)[Saint Mawes]Mawes.

During the Renaissance, new forts built to secure key positions were large enough to resist the increasingly large armies that moved across Europe. When the Europeans arrived in America, they secured their hold on the land whenever possible with the newest type of stone fortifications. Otherwise, they relied on wooden stockades not much different from those used in the Middle Ages. The most interesting transfer of technology occurred in the sixteenth century, when the Portuguese helped the Ethiopians build castle-like fortifications at Gonder in northwestern Ethiopia. The influence of the new Renaissance techniques began in Africa;fortsAfrica with Portuguese forts from Ceuta (1415) to Mozambique (1506) and in Asia from Goa (1510) to Malaca (1511).

Seventeenth and Eighteenth Centuries: Vauban and Bastioned Forts

The seventeenth and eighteenth centuries marked the great age of “scientifically designed” fortifications. The masters of the art perfected their designs based on mathematical calculations, only modifying final plans to match the terrain. During this period, the Bastionsbastion, with two fronts and two flanks attached to the curtain walls, became the dominant feature. Additional outworks were added for protection. The wide, deep moat acquired additional protective positions, low walls rose from its base, and a Glacis (slope)glacis, or gentle slope, was created to provide clear fields of fire.

During the sixteenth century the Italians lost their dominance in the field of military architecture and were replaced by the Germans, the Dutch, and the French, who developed their own schools of fortifications. The Dutch mathematician Simon Stevin, SimonStevin, SimonStevin (1548-1620) wrote a treatise on defenses, emphasizing the use of water features.

The French school included such masters as Jean Errard de Bar-le-Duc, Jean Errard deBar-le-Duc, Jean Errard de[Bar le Duc, Jean Errard de]Bar-le-Duc (1554-1610), who built a number of fortifications and in 1600 published a treatise on design in which he warned against reliance on geometrical calculations over design to suit the terrain. In 1640, Blaise François, comte de Pagan (1604-1665), emphasized the importance of the bastions and the use of detached bastions and outworks, including listening galleries to deter mining operations against the walls. Sébastien Le Prestre de Vauban, Sébastien Le Prestre deVauban, Sébastien Le Prestre deVauban (1633-1707), considered a genius of military Engineers;Frenchengineering, emerged in the age of French domination, during the reign of Louis XIV (1638-1715).

Vauban based much of his work on that of Pagan but also emphasized the use of detached bastions, claiming that their fall would not result in the loss of the entire fort. One of the best examples of Vauban’s first system of fortification is the citadel of Lille citadel (France)Lille, in northern France. Vauban later refined his first system with a second and a third, and an example of the latter can be seen in Neuf Brisach, built in 1699 in northeastern France. One of Vauban’s contemporaries, the Dutch solider and military engineer Baron Menno van Coehoorn, Menno vanCoehoorn, Menno vanCoehoorn (1641-1704), developed a system in the Netherlands that was adapted to water defenses and was much more economical to build than were fortifications of Vauban’s second and third systems. Although they designed many fortifications, Coehoorn and Vauban were masters of the siege and knew that no fortification was impregnable.

Some of the important features of the bastioned fortifications of the Vauban era included the bastion, bonette, caponier, casemate, counterguard (a ravelin with a redoubt), counterscarp, covered way, crown work, detached bastions, glacis, hornwork, lunette, ravelin, and tenaille, which were used to protect the curtain.

The new fortifications in France and some other countries also defended key ports, forming coastal defenses; others guarded mountain passes; others still were incorporated in a loose line covering the exposed frontier. There were no solid lines of defenses, but an army of the period would have had either to eliminate these positions or to leave its lines of communications exposed. Many older fortifications still remained in service, and some played a prominent role in conflicts such as the English Civil War of 1642-1651.

The eighteenth century did not bring any major changes in fortifications design. In the mid-eighteenth century, John Muller, JohnMuller, JohnMuller (1699-1784) published in England A Treatise Containing the Practical Part of Fortification (1755), which explained the design elements of Vauban’s and Coehoorn’s systems, among others. French military engineer Marc-René de Montalembert, Marc-René deMontalembert, Marc-René de Montalembert (1714-1800) emphasized the use of artillery for defense of fortifications and insisted that protecting the guns in casemates was the best policy.

Nineteenth Century Transition

A transitional phase began late in the eighteenth century when the threat of French invasion lent a new importance to coastal Coastal defensesdefenses in England. Naval action against a strong tower in Corsica in 1793 led the British to create similar towers to defend their vulnerable coastline. More than one hundred of these circular brick Martello Martello towersTowerstowers were completed between 1805 and 1812. With thick walls at the base and rising to a height of about 10 meters, they held an artillery piece protected by a parapet on the roof. Martello towers were also built in North America and South Africa.

Interesting innovations appeared in the first half of the nineteenth century. WallsWalls were made slightly higher to add more positions for cannons at different levels. Some examples include the Maximilian Maximilian towerstowers built at Linz, Austria, in 1830 and later near Verona, Italy, which consisted of three floors and eleven mounted guns. The Malakov Malakov TowerTower of Sevastopol, Ukraine, mounted guns on two floors and the roof, and the pentagonal Fort Sumter in the harbor of Charleston, South Carolina, accommodated artillery on two floors and the roof.

The Prussian school of fortifications adopted the earlier ideas of Montalembert, opting for a polygonal design and replacing bastions with Caponier (Prussion fortification) caponiers that protected the ditches and became essential in covering the faces of the forts. The masonry forts of the nineteenth century proved inefficient in the American Civil War American Civil War (1861-1865);fortifications (1861-1865) when Forts Fort Sumter, fall of (1861) Sumter and Fort Pulaski Pulaski proved vulnerable to rifled artillery. The Americans soon came to rely on wood and earthen forts, such as Fort Fort Wagner Wagner in Charleston harbor, South Carolina, to withstand heavy bombardment. After the Franco-Prussian War (1870-1871) both the French and Germans also reconsidered their designs.

Late Nineteenth Century

Raymond Adolphe Seré de Rivières, Raymond Adolphe Seré deRivières, Raymond Adolphe Seré de[Rivieres, Raymond Adolphe Sere de]Rivières (1815-1895) initiated new polygonal designs with surrounding ditches to secure France’s borders, forming an almost continuous line defended by fortress girdles and barrier forts in restricted terrain. German military strategists did the same for Germany’s borders, emphasizing the use of detached polygonal forts to form a fortress girdle around key cities. These forts served as artillery platforms and were located well beyond the town’s perimeter to keep modern long-range artillery out of range. By the mid-1880’s, the French had developed a new high-explosive shell that rendered all existing forts obsolete. All masonry forts had to be reinforced with concrete. Many of the newly outdated German forts and exposed artillery positions were replaced with detached battery positions. Interval works were created to fill the gaps in the rings. The new forts were built with concrete instead of bricks and reinforced with armor.

A sectional diagram of the Maginot line, defensive fortifications built along France’s eastern border to protect against German invasion.

(Hulton Archive/Getty Images)

Both France and Germany adopted armored galleries and Turrets;armoredturrets for their Artillery;fortifications forartillery in the 1870’s, but it was not until the 1890’s that these became the essential artillery positions of key forts. The German Gruson Gruson WorksWorks, founded in 1869 and later absorbed by Krupp, became a primary supplier of armored turrets to Germany and other countries, such as Switzerland. The French used turrets built at Saint-Chamond in southeast-central France. The new French forts also included armored observation positions and machine-gun turrets with Bourges casemates designed for flanking fire and mounting 75-millimeter guns. Belgian military Engineers;Belgianengineer Henri-AlexisBrialmont, Henri-AlexisBrialmont, Henri-AlexisBrialmont (1821-1903) created a fortified ring at Antwerp, and more modern rings, with forts that included a central citadel with artillery turrets enclosed by a moat, at Namur and Liège. In the last decade of the century, the Germans created a new type of fortification called the Feste (German fortification)Feste, which included large garrison areas and artillery blocks mounting several turreted guns. The first Feste was built at Mutzig. Several more were built around Metz and Thionville, but none saw combat until World War II. Across the border, the French continuously modernized their forts, forming fortress Girdles (fortifications) “girdles” at Verdun, Toul, Épinal, and Belfort. During World War I the Germans based their strategy on maintaining their defensive positions in France, going through Belgium, avoiding the French fortifications, and using their new super-heavy 420-millimeter artillery to smash the weaker Belgian forts built by Brialmont. In 1916 a change in strategy led the Germans into a disastrous campaign against the heavily defended Verdun forts, which had a telling effect on postwar considerations.

Twentieth Century

In the 1930’s, influenced by the Verdun experience, the French built the Maginot Maginot lineline, a line of defensive fortifications covering the eastern border of France. The new forts, known as Ouvrage (French fortification)ouvrages, reflected not only the lessons learned at Verdun but also the influence of the German Feste, now located in France. These ouvrages mounted medium artillery in turrets and casemates in individual blocks and had a subterranean service and garrison area linked to the combat area by a main gallery of up to 1 kilometer in length. The forts, with concrete roofs of up to 3.5 meters high on subterranean positions up to 30 meters deep, could resist rounds of up to 420 millimeters.

The Germans also built subterranean forts on their East Wall in the 1930’s, but after 1936 they created a new type of fortified line, the West West Wall (German fortification)Wall, which used smaller bunkers deployed in depth and protected by massive minefields. The Italians created a new line of Alpine fortifications known as the Vallo Vallo Alpino (Italian fortification)Alpino, and the Swiss created similar, smaller positions to defend their National National Redoubt (Swiss fortification)Redoubt with only a few modern, smaller versions of Maginot-style forts on the border. The Czechs, with French assistance, created a line of fortifications to encircle their vulnerable border, one section of which included Maginot-style ouvrages. Even the Belgians built a series of new forts to defend Liège from German attack. The Soviets created the Stalin line, with numerous positions similar to those on the Swiss and Czech lines, but abandoned it in 1940 for another line that was not completed. The Finns built a line of small fortifications called the Mannerheim Mannerheim line line, with small bunkers and obstacles, and, after its loss, built a stronger position called the Salpa Salpa line line. The longest defensive line, the Atlantic Atlantic Wall (German fortification) Wall, was created by the Germans between 1941 and 1944. It stretched from the Spanish border along the coast through Norway. This was not a continuous line but included many “fortress zones” built around ports with smaller strongpoints. Bunkers, mines, artillery positions, and other obstacles defended possible landing sites. In addition, the Germans built special concrete positions for heavy artillery on coastal sites, huge fortified submarine pens, command posts, and shelters in the lands they occupied. Their opponents built similar positions before and during World War II, from the English coast to Gibraltar and Singapore and from the American coast to the entrance to Manila Bay.

After World War II, the heavily defended gun-bearing fortifications forming continuous defensive lines were largely abandoned in favor of smaller strongpoints and lighter border defenses. The Cold Cold War (1945-1991);fortificationsWar led to a new generation of fortifications that were created largely to protect command centers, such as the Air forces;U.S.U.S. Air Force command center at Cheyenne, Wyoming. Some older fortifications, such as a few Maginot ouvrages, were restored for that purpose. Underground missile Missile silossilos were constructed to protect nuclear missiles. However, when conventional war broke out most armies relied upon fortified lines consisting of field fortifications, fortified strongpoints, and even trenches. Such was the case in the Korean and Vietnam Wars, and in the 1990’s, when the Iraqis built defenses on the border of occupied Kuwait.Fortifications;modern

Books and Articles
  • Brice, Martin Hubert. Forts and Fortresses: From the Hillforts of Prehistory to Modern Times, the Definitive Visual Account of the Science of Fortification. New York: Facts On File, 1990.
  • Chartrand, René. The Forts of New France in Northeast America, 1600-1763. Illustrated by Brian Delf. Botley, Oxford, England: Osprey, 2008.
  • Clements, W. H. Towers of Strength: The Story of the Martello Towers. South Yorkshire, England: Leo Cooper, 1999.
  • Duffy, Christopher. Fire and Stone: The Science of Fortress Warfare, 1660-1860. London: David and Charles, 1975.
  • Dunstan, Simon. Israeli Fortifications of the October War, 1973. Illustrated by Steve Noon. Botley, Oxford, England: Osprey, 2008.
  • Field, Ron. American Civil War Fortifications: Mississippi and River Forts. Illustrated by Adam Hook. Botley, Oxford, England: Osprey, 2007.
  • _______. Forts of the American Frontier, 1820-91: The Southern Plains and Southwest. Illustrated by Adam Hook. Botley, Oxford, England: Osprey, 2006.
  • Griffith, Paddy. The Vauban Fortifications of France. Illustrated by Peter Dennis. Botley, Oxford, England: Osprey, 2006.
  • Hogg, Ian. The History of Fortification. New York: St. Martin’s Press, 1981.
  • Hughes, Quentin. Military Architecture. London: Hugh Evelyn, 1974.
  • Kaufmann, J. E., and Robert Jurga. Fortress Europe. Conshohocken, Pa.: Combined, 1999.
  • Kaufmann, J. E., and H. W. Kaufmann. Fortress America: The Forts That Defended America, 1600 to the Present. Illustrated by Tomasz Idzikowski. Cambridge, Mass.: Da Capo Press, 2004.
  • Stephenson, Charles. The Fortifications of Malta, 1530-1945. Illustrated by Steve Noon Botley, Oxford, England: Osprey, 2004.
  • Weaver, John R. II. A Legacy in Brick and Stone: American Coastal Defense Forts of the Third System, 1816-1867. McLean, Va.: Redoubt Press, 2001.
Films and Other Media
  • Last of the Mohicans. Feature film. Morgan Creek Productions, 1992.
  • Modern Marvels: Atlantic Wall. Documentary. History Channel, 1999.
  • Modern Marvels: Forts. Documentary. History Channel, 1999.
  • Modern Marvels: The Maginot Line. Documentary. History Channel, 2000.
  • Vincennes. Feature film. Chronicles of America Pictures, 1923.

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