MILITARY GEOGRAPHY
FOR PROFESSIONALS AND THE PUBLIC
13. FORTRESSES AND FIELD FORTIFICATIONS
[Eban Emael] served as the southern anchor of the Albert Canal Line, and . . . ranked among the most important single defensive positions in Europe. . . . Ten minutes after the [German glider] landings, all installations and guns on top of the fort were wrecked.
John R. Galvin
Air Assault
BELGIAN FORTRESS EBEN EMAEL BARRED THE WAY BETWEEN GERMANY AND THE ENGLISH CHANNEL WHEN Hitler launched a large-scale offensive on May 10, 1940.1 That bastion quickly succumbed to a small-scale glider assault because its architects, contrary to good advice from Carl von Clausewitz in his opus, On War, failed to incorporate credible active with passive defenses, failed to "present a front on every side" (of which there have been five instead of four since the advent of air power), and above all failed to "recognize the fact that the enemy, in avoiding the unconquerable parts, will alter the whole pattern of his attack."2 Future designers of forts and field fortifications would do well to heed those wise words.
PRECEDENTS AND PROGNOSES
The earliest earthen fortifications predate written human history, which notes a massive wall, a deep ditch, and adjoining tower at Jericho circa 7000 B.C.3 Concepts and construction techniques thereafter evolved from simple to complex over several millenia that saw reinforced steel and concrete replace wood, brick, and stone blocks as preferred materials. Legendary Crusader castles, built to protect Christian outposts from Saracens in the Holy Land, typify fortified points. Hadrian's Wall in ancient Britannia and the Great Wall of China, both of which were buffers between "civilized" communities and barbarians, exemplify fortified lines.4 The utility of those relics now is nearly nil, and siegecraft patterned after Vauban is no longer popular,5 but well-designed forts and field fortifications likely will remain useful in the 21st century, whether they are simply hardened shells or defenses in great depth.
FORTIFIED POINTS
Impromptu strong points may be as basic as foxholes dug with D-handle shovels or buildings embellished by sand bags, razor wire, land mines, and flares, whereas elaborate counterparts commonly include ramparts, casemates, carapaces (like turtle shells), and revetments constructed of iron, steel, concrete, stone slabs, and bricks. Armed forces benefit from both.6
IMPROMPTU STRONG POINTS
Famous points fortified extemporaneously include the Alamo in San Antonio, TX, where Colonel William Barrett Travis, Davy Crockett, Jim Bowie, and 185 other men on March 6, 1836, fought to the death against onslaughts by a force that numbered about 4,000 under Mexican General Santa Anna. Actions at Rorke's Drift on the Buffalo River in Natal had a happier ending for defenders --11 heroes received Victoria Crosses after fewer than 100 able-bodied men led by British Lieutenants John Chard and Gonville Bromhead converted Otto Witt's mission station into a makeshift fort, then held off 4,000 of King Cetshwayo's fearsome Zulu warriors during the long, bloody night of January 22-23,1879.7
Rubble heaps that result from aerial bombardments, artillery barrages, and house-to-house combat in urban areas unintentionally furnish defenders with ready-made fortresses. Clever improvisations on countless occasions have converted partially destroyed cities into impromptu strong points, of which Leningrad, Stalingrad, Manila, Seoul, and Hué were among the most widely publicized.
ELABORATE STRONGHOLDS
Early U.S. armed forces and pioneers, who were masters at improvisation, built relatively elaborate military forts and palisaded civilian settlements to protect themselves and their property as they marched from east to west and coast to coast across America.8 National leaders elsewhere did likewise to defend against invaders.
Coastal Fortifications. Coastal defenses reached their zenith during the 19th century, when casemated artillery batteries guarded port cities and other key terrain features against onslaughts from the sea. The Star Spangled Banner still waved over Fort McHenry after a British fleet failed to land redcoats in Baltimore harbor on the night of 25-26 August 1814 and the U.S. Civil War opened at Fort Sumter, South Carolina, 47 years later (August 1861). Coastal fortifications around the world continue to serve useful purposes under favorable circumstances, but their Golden Age closed with the advent of offensive firepower that makes new construction seem cost-ineffective.9
Fortified Islands. Small islands make admirable fortified points, as ingenious Japanese armed forces demonstrated on every island they intended to hold in the Western Pacific during World War II, whether the terrain was flat and open or highlands honeycombed with caves. Withering fire met U.S. Marines on tiny Betio Island (Tarawa atoll), where underwater obstacles and mines barred the way to beaches. Shorelines there bristled with more than 500 interconnected blockhouses, bunkers, pillboxes, and breastworks encased in concrete reinforced with steel rods and splinter-proof coconut logs, then covered with up to 10 feet (3 meters) of sand or crushed coral, an amalgam that was practically impervious to pounding by carrier-based aircraft and big naval guns. Bloody fighting that ensued at point-blank range, much of it with satchel charges and flamethrowers, was replicated on Saipan, Peleliu, Iwo Jima, Okinawa, and other islands, each of which was a fortress in every sense of the word.10
Solitary Forts Inland. Solitary forts located inland became increasingly sophisticated after two German "Big Bertha" (16-inch, 42-centimeter) howitzers demolished Belgian redoubts around Liège during a 4-day bombardment in August 1914. The most formidable, however, lacked mutually supporting fields of fire, could neither be reinforced nor resupplied if surrounded, and were vulnerable to vertical envelopment, as defenders at Eben Emael discovered. The last large-scale construction commenced before World War II.11
Earthen Labyrinths. No nation or subnational group has ever created earthen labyrinths as elaborate as those that Viet Cong guerrillas constructed in South Vietnam for use as headquarters, hideouts, air raid shelters, storehouses, dormitories, kitchens, classrooms, arms factories, hospital operating rooms, recovery wards, theaters, and rest centers. Construction, begun in the 1940s at the onset of serious Indochinese uprisings against French rule, took advantage of laterite soils which were almost impervious to water and very hard, especially where taproots near the surface strengthened tunnel ceilings like steel reinforces concrete. Embellishments, all dug by hand a few feet per day, continued during the next three decades until multilevel mazes north of Saigon featured concealed entrances and exits, chambers, galleries, bunkers, air shafts, crude elevators, and wells that were interconnected by twisty-turny passageways replete with false leads, dead ends, and secret trap doors designed to repel chemical warfare agents and reduce the range of underground blasts.12
U.S. intruders, called "tunnel rats," all volunteers armed mainly with pistols and knives, ventured into those claustrophobic confines where they battled with ingenious foes, poisonous snakes, scorpions, giant spiders, and bats in booby-trapped darkness that flashlights barely illuminated. Their searches uncovered huge caches of hand grenades, automatic weapons, ammunition, and rice, while Rome Plow bulldozers stripped vegetative cover overhead, demolition specialists sent shock waves down corridors, and riot control agents polluted crawl spaces. Tunnel warfare nevertheless continued apace for 5 years until carpet-bombing B-52s finally collapsed most installations shortly before U.S. Armed Forces departed.13
Fortified Areas. Fortifications that sprawl many miles in every direction, like point defenses just discussed, may be simple or complex. The German Wehrmacht, whose winter offensive of 1942-1943 left nearly a million Soviet troops inside a massive salient west of Kursk, encountered what may have been the most awesome array of field fortifications ever built when they launched Operation Zitadelle on July 4th to cut off that bulge at its base. The Red Army's principal works, about 12 miles (20 kilometers) wide, consisted of two fortified zones, each of which contained three successive positions buttressed by trenches (aggregate length about 1,250 miles or 6,000 kilometers), antitank ditches, pillboxes, bunkers, barbed wire entanglements, and 1,000,000 mines, all on terrain laced with water-filled ditches. Additional obstacles behind the two main lines of resistance blocked avenues most vulnerable to breakthroughs. German drives soon stalled, Soviet forces counterattacked on July 12th, and most divisions trapped inside the salient lived to fight another day, despite stupendous casualties on both sides.14
FORTIFIED LINES
Fortified lines, which incorporate all assets and avoid most shortcomings of isolated forts, have been fashionable since Domitian, Trajan, and Hadrian erected walls along the outer limits of the Roman Empire in the 1st and 2nd centuries A.D.15 Sir Winston Churchill, pontificating in Fulton, Missouri, on March 5, 1946, noted that "from Stettin in the Baltic to Trieste in the Adriatic an iron curtain has descended across the [European] continent." That edifice, built to keep Warsaw Pact citizens from fleeing repressive regimes, was unusual as well as ugly, because defense against aggression is the purpose of most fortified fences.
Many linear fortifications in the latter category have been impressive: Confederate diggings around Richmond and Petersburg, Virginia, in the 1860s; trenches that lined the Western Front in Europe during World War I; the Mannerheim Line along the Russo-Finnish frontier in 1939-1940; the Gustav and Winter Lines in Italy, 1943-44; the Mortise Line that French Armed Forces built along the Tunisian border in the 1950s to keep support from reaching rebels in Algeria; and extensive fortifications that still stand along the Korean demilitarized zone immediately come to mind. None, however, rivaled the complex structures that France and Germany constructed and occupied with differing degrees of success during World War II.
THE MAGINOT LINE
The Maginot Line, an architectural marvel partly hewn from solid stone, ran 560 miles (900 kilometers) along the Franco-German frontier from Switzerland to the Ardennes Forest by the Belgian border, where it terminated for lack of funds and a high water table in Flanders. Large, self-contained works (ouvrages), connected by tunnels and railways, contained fixed and retractable cupolas, two-tiered pillboxes, ferro-concrete blockhouses, fireproof armored doors, air intakes, exhaust vents, and gas filters near the surface, with living quarters, mess halls, magazines, communication centers, and power supplies disposed well below. Barbed wire entanglements, mines, and antitank traps completed the complex. Resultant installations, in the words of Marshal Henri Philippe Pétain, assured "minimum danger and maximum comfort," all to little avail: German Blitzkriegs through Belgium and Holland in May 1940 maneuvered around the Maginot Line without hitting it head on. Some enterprising farmers in Alsace-Lorraine later bought a few blockhouses with dark, damp cellars, where they still grow mushrooms for grateful French chefs.16
THE SIEGFRIED LINE
The so-called Siegfried Line (Westwall), which shielded Germany's industrial heartlands against invasions from the Low Countries, Luxembourg, and France, was less ambitious but, unlike the Maginot Line, necessitated frontal attacks because it was much harder to outflank. Row after seemingly endless row of fearsome Dragon's Teeth with minefields for fillings dared U.S. tank commanders to trespass. Two fortified belts rather than one, together with natural obstacles such as the Rhine, Roer, and Kyll Rivers, afforded depth in front of the Ruhr and Saar-Palatinate. Serious efforts to penetrate ceased for several months after U.S. Armed Forces in hot pursuit punched one sizable hole in October, 1944, then literally ran out of gas. Tremendous concentrations of power on narrow fronts tore through the following March, but not before slugging matches spilled barrels of blood on both sides-- "Bitche was a bitch" was the way one trooper put it after breaching stubborn defenses around that Alsatian stronghold.17
THE ATLANTIC WALL
An impregnable wall along the Atlantic coast from northern Norway to the Pyrenees Mountains was a figment of Hitler's imagination, but the segment between Calais and Cherbourg, France, was indeed a troublesome stretch after Field Marshal Erwin Rommel took charge in November 1943. "Believe me, Lang," he told his aide, "the war will be won or lost on the beaches. We'll have only one chance to stop the enemy, and that's while he's in the water . . . struggling to get ashore."18
Improvements proceeded at a feverish pace while half a million laborers poured so much concrete that little was left elsewhere in Western Europe. Flat-faced structures took precedence over curved surfaces to save time. They used steel sparingly, since it was in short supply, but builders cannibalized parts of the Maginot Line to compensate. More than 9,000 strong points appeared, some with walls up to12 feet thick (3.6 meters). Rommel personally designed medieval-like obstacles and emplaced half a million astride high water marks before D-Day: concrete tetrahedrons, Czech hedgehogs that consisted of three railway rails set in concrete at right angles, and telephone pole-sized stakes pointed seaward, some capped with land mines or tipped with "can opener" blades to rip the bottoms off landing craft. Other mines by the millions covered beach exits, anti-airborne "Rommel asparagus" stakes strung together with trip wires discouraged glider landings in open fields, and deliberately flooded lowlands impeded movement from landing sites inland. Most fortified resort hotels and summer homes could sweep beaches at point-blank range with overlapping automatic weapon and artillery fire.19
General Eisenhower, with last-minute misgivings before the D-Day assault, scribbled a note to himself that read, "Our landings in the Cherbourg-Havre area have failed to gain a satisfactory foothold and I have withdrawn the troops . . . . If any blame or fault attaches to the attempt, it is mine alone."20 Allied forces, of course, seized lasting lodgments on June 6, 1944, at less cost in lives than the most optimistic predictions, despite touch-and-go situations in the U.S. sector, where First Army's after-action report recorded 1,465 dead, 3,184 wounded, 1,928 missing, and 26 captured on what became known as "the longest day."
OFFENSIVE FORTIFICATIONS
Security always has been, and still is, the primary function of fortifications, but tunnels that go under rather than over, around, or through enemy positions occasionally appeal to devotees of strategically and tactically indirect approaches that take devious paths to achieve objectives through surprise.
SUBTERRANEAN EXPLOSIVES
Offensive armed forces balked on the surface have long burrowed beneath enemy positions to inflict damage, a classical siegecraft technique. Belligerents on the Western Front during World War I applied that practice on a scale never duplicated before or since. The biggest blast behind or under enemy lines erupted in Belgium between Ypres and Warneton on June 7, 1917, when Australians and Canadians at 11 sites along an 8-mile (13-kilometer) stretch of Messines Ridge detonated 933,000 pounds of explosives (466 tons), mainly ammonol. No official estimate of German casualties ever was released, but 10,000 men were missing and 7,350 were prisoners of war when the battle was over.21
SUBTERRANEAN SPEARHEADS
Investigators in the Republic of Korea (ROK), alerted by suspicious subterranean explosions, found three large tunnels in the mid-1970s and a fourth in 1990, each deeply embedded beneath the mountainous demilitarized zone and each large enough to accommodate quarter-ton trucks together with enemy troops four abreast. Searches for 16 more along that 155-mile (250-kilometer) demarcation line continued in response to further audible rumblings, information derived from sensors, and North Korean defectors. ROK officials all the while feared that if war occurred North Korean light infantry, commandos, and other special operations forces would pour through, surround Seoul, cut off reinforcements, sever supply lines, and form a second front south of the DMZ. Speculators alternatively suggested that decisionmakers in Pyongyang might deposit nuclear weapons at mid-point in one or more tunnels, detonate them when windborne fallout from subsurface bursts would drift south, then launch a full-scale offensive through cracked coalition lines while confusion reigned and electromagnetic pulse blacked out U.S. and ROK radio communications as well as computers. Eruptions along Messines Ridge would seem minor in comparison.22
FORTIFICATIONS IN THE NUCLEAR AGE
The advent of the Nuclear Age increased the value of subterranean fortifications by some orders of magnitude, because the strongest installations on or near the surface simply could not survive assaults by accurate weapons with yields measured in kilotons (much less megatons).
MILITARY "HARDENING" PROGRAMS
Neutrals as well as potential belligerents sought sanctuaries beneath bedrock. Sweden, for example, early on created a gigantic cavern with more than 1,000 rooms and tunneled from shorelines into mountainsides to shelter its fleet.23 The United States and the Soviet Union installed intercontinental ballistic missiles (ICBMs) in silos, some of which could withstand overpressures of 10,000 pounds (4,535 kilograms) per square inch, but super lethal weaponry outclassed super hardening. Senior officials of North American Air Defense Command (NORAD), ensconced in the bowels of Cheyenne Mountain near Colorado Springs, often wondered whether a huge direct hit would vaporize their headquarters despite blast-proof doors and several thousand feet of overburden. How well such shelters might have worked will never be known, because none ever were tested in combat, but most students of nuclear war are skeptical about survival prospects.24
CIVIL DEFENSE PROGRAMS
The Berlin crisis of 1961 precipitated the first U.S. civil defense shelter program, but only half the sites in existing structures ever were marked or stocked with rudimentary survival kits. Half of those were located in business districts that were heavily populated only during daylight hours and empty on weekends as well as holidays. All save the most avid advocates soon lost interest in do-it-yourself family shelters, which were widely advertised in the early 1960s, but never became numerous.25
Soviet emphases on civil defense conversely were strong throughout the Cold War. Urban planners accordingly sought to restrict population densities, develop satellite towns around large cities, and create firebreaks. Some contemporary sources cited new production facilities, dispersed and hardened. Soviet programs reportedly included actions to replace glass with solids; fireproof roofs; reinforce weak structures; and improvise shields for or bury selected utility stations, plus power and water conduits. Redundant structures and stockpiles were standard procedures. U.S. defense analysts agreed that such plans were imposing on paper, but extents to which they were implemented remain debatable.26
CITADELS VERSUS CW AND BW WEAPONS
Chemical and biological warfare (CW, BW) agents that creep into nooks and crannies can overcome occupants of citadels able to survive the blast, heat, and radiation that accompany high-yield nuclear detonations, unless secure ventilating systems and vapor locks safeguard every entry. Surefire protective measures are conceivable, but are costly to install.
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