How armies build better bridges

Brits build better bridges; certainly they can build them quickly, under difficult conditions. Route 3 commuters today might think about military bridging as they creep past the Route 228 temporary bridge project in Rockland. In Iraq, American GIs erect two-lane, heavy-duty bridges quickly; they built a pair across the Kazer River in three days, working mostly by hand. But the state highway job in Rockland appears to be something else altogether.

Advancing armies have long confronted the problem of bridges destroyed by defenders. A ruined bridge temporarily halts an army, even if some soldiers can clamber down and then up the sides of a ravine or canyon, or ford a river. Armies need food to fight well, and destroyed bridges stop the movement of supply wagons. After about 1600, generals discovered that cannon not only sink in rivers, but also bog down in mud and prove almost impossible to drag up hillsides. As weapons grew heavier and more cumbersome, burning or blowing up bridges proved more and more effective.

Intrepid generals now and then crammed men into boats and crossed rivers, with tethered horses swimming alongside. On Christmas Eve 1776, Washington moved 2,400 Continental soldiers across the half-frozen Delaware and surprised the partying Hessians in one of the first American victories of the war. Six years later, General Francis Marion, called the Swamp Fox by his British foes, crossed the Santee and defeated a garrison of Redcoats. While small, determined forces flitted almost Indian-like across rivers and steep valleys, moving artillery meant Herculean effort. Fort Knox honors in its name the staggering accomplishment of General Henry Knox, who brought British cannon captured at Ticonderoga by sledge across frozen New England to be fired against the British occupying Boston. At the time the feat seemed a marvel of military engineering.

Horses and mules not only swim, but also climb hills well and even flounder through swamps. Mules especially prove calm not only in battle, but also off the beaten path. For decades the Army and Marines used them as pack animals in part because they followed troops anywhere. Mules can carry heavy loads crosswise along steep slopes. Unlike horses, which often rear and neigh in alarm, when mules begin to lose their footing they freeze, look around, keep quiet, and think. Military historians and Hollywood glorify the cavalry, but the mules of the quartermaster corps helped win many battles. Often mules carried the heavy machine guns troops used to pin down enemy soldiers firing at engineer units attempting to repair or rebuild bridges.

As armies mechanized during World War I, a handful of military officers glimpsed the impact of airplanes on tanks. They assumed that soon airplanes would bomb bridges ahead of tanks, and slow down armies wholly dependent on trucks, tanks, and other machinery. In the 1930s, as automobiles pulled passengers from trains, young officers realized that fast-moving military vehicles might transform old attack and defense strategies based on mules and railroads. World War II proved them right, especially when German tanks advanced so quickly that defending armies had no time to blow up bridges. Only the Dutch, who opened their dikes and flooded roads, slowed down the blitzkrieg, the lightning war.

An obscure British civil servant accurately foresaw that any invasion of Europe would involve rebuilding bridges, usually under fire. Donald Bailey worked out a way of building bridges from pieces, presented his invention to his superiors, and by 1944 transformed the war effort.

Bailey designed bridges to be built from standardized sections, with no piece heavier than six men could lift. Components had to fit in 3-ton British trucks, or the deuce-and-a-half trucks used by GIs.

In 1942, Allied troops erected a 440-foot-long suspension Bailey Bridge across the Shelia River in Burma. Working by hand, the job took 30 days.

GIs and British Tommies built Bailey Bridges, often under fire, to speed the Allied invasion of Europe. Six hundred and twenty-nine 3-ton trucks delivered 1,900 tons of components to a site on the River Po in Italy. Seven days later, soldiers had finished a massive, solid bridge, assembled by hand. After the war, President Eisenhower praised the Bailey Bridge as one of the greatest Allied triumphs. Bailey received a knighthood, and continued to live quietly.

World War II taught American generals that a postwar weapon, the Military and Interstate Highway System, must be designed for quick repair after aerial bombing. Motorists rarely notice that almost all interstate bridges are remarkably similar, and that Route 3 and other roads built roughly to interstate standards have nearly identical bridges. In wartime, the US Army Corps of Engineers expects to replace bombed-out bridges rapidly.

In 1983, when a section of a bridge on Interstate 95 in Connecticut collapsed, federal authorities had the road open within two weeks. Only rarely do motorists recall that the interstate highway system is a Cold War weapon, and that American weapons work, even when damaged.

Route 3 motorists crawling past the temporary bridge site in Rockland figure out that the two existing spans need rebuilding. The temporary span erected between them will carry northbound, then southbound traffic, while crews destroy and rebuild the northbound, then the southbound, bridge.

But building temporary bridges goes a bit faster in Iraq. The journalist who visited the Kazer River site found matters in the charge of a sergeant in the 326 Engineer Battalion based at Fort Campbell in Kentucky. He had an excavating machine to help things along, but his men did about everything by hand, more as a training exercise against the day when they would be shooting at snipers while lugging components forward. The villagers had turned out to see the pair of old bridges blown up, and a few had stayed to watch the unhurried, methodical, but incredibly rapid building of two two-lane bridges capable of carrying the heaviest vehicle in the Army, the 70-ton Abrams tank. The sergeant looked forward to the next mission, erecting a new support weapon, the Dry Support Bridge, like the Bailey Bridge developed in Britain by an army as inventive as the American one.

Almost certainly the schoolchildren of Rockland will not be bused to a safe spot near Route 228 to watch contractors blow up one of the existing spans. What might be one lesson the students would never forget will not happen, because contractors will dismantle each existing bridge piecemeal, probably using jackhammers that will make a racket for days.

It might be nice to see whether civilians can erect a three-lane military temporary bridge in three days, perhaps with the aid of heavy equipment. But it might be even nicer if military bridge-building methods were applied to a large number of other bridge repair projects in this area, all of which take longer than three days each. Americans forget what GIs did in World War II, when the United States hustled.

Norwell resident John Stilgoe is Orchard Professor in the History of Landscape at Harvard.