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The Dew Line

A radar station near the northeast corner of Alaska, once part of the front line of the Cold steinmetz/corbis2007_4_32

In the early hours of April 17, 1952, World War III nearly began—although not many people realized it at the time.

The previous afternoon an intelligence source had reported unusual levels of activity at Soviet air bases. Shortly after midnight U.S. Air Defense Command headquarters, in Colorado Springs, got word from Alaska that vapor trails from “bogeys” (unknown aircraft) had been sighted high over the Bering Sea, coming from the direction of the Soviet Union. As shaken generals fretted over the report, another message arrived: Five more bogeys had been sighted off the coast of Maine. It looked as if this might be the real thing—an atomic sneak attack. Commanders ordered a full-scale alert. Fighters were scrambled and Air Force bombers prepared for a retaliatory strike.

And then nothing happened. The vapor trails over Alaska disappeared, along with the supposed enemy bombers. The unknowns over Maine were identified as off-course civilian airliners. Faster than it had begun, the threat vanished.

Although the people of North America slept undisturbed through the incident, it was ice water in the face for the military. It was bad enough that the U.S. defense network had been brought to the brink of war by such flimsy evidence. Much worse, though, was that it had taken 90 minutes for the first report of enemy planes to make its way up the chain of command to those in charge, and even longer to figure out what was actually going on. The mechanisms in place to spot, report, and confirm sightings of unknown aircraft were more suited to the Battle of Britain than the jet age.

How could America tell the difference between a real enemy attack and an apparent one? In the aftermath of the 1952 incident the defense establishment studied this question intently, and a big part of the answer turned out to be the Distant Early Warning Line—the DEW Line, for short—a string of radar stations along the very edge of civilization in one of the most desolate, hostile, cold, and empty places on earth.

The DEW Line project began at a gathering of eminent scientists and engineers called the Lincoln Summer Study Group. In the summer of 1952, at the behest of the Air Force, it met at MIT’s Lincoln Laboratory (where radar had been invented) to examine air-defense issues. Among the conferees were J. Robert Oppenheimer and I. I. Rabi, both Manhattan Project veterans—men accustomed to thinking big and solving intractable problems.

It was elegant and simple in theory. Putting it into practice would be a very different matter.

Even before 1952 the United States had begun to improve its air-defense effort. A postwar radar network called Lashup, deployed around some major cities, was being beefed up, and two radar fences were under construction: the Pine Tree Line, along the U.S.-Canadian border, and the unstaffed Mid-Canada Line, farther north near the fifty-fifth parallel. These were useful against slow-moving propeller-driven planes but inadequate for the jet age. As the Lincoln group pointed out, by the time Soviet jets crossed these thresholds, it would be too late to stop them. Only by detecting intruders earlier could an attack be thwarted.

The Lincoln group also knew that the shortest route for Soviet bombers approaching the United States would be across the North Pole. Such an attack could be detected only by constructing radar stations in the far north, stretching across the top of the Western Hemisphere inside the Arctic Circle from Alaska to Greenland, covering the entire airspace and connected to the United States by reliable communications. Such a network could provide up to four hours’ warning to prepare defenses and (it was hoped) evacuate at least some of the populace from target cities.

The concept was approved by President Harry S. Truman in December 1952 as one of his last acts in office. Over the next year it was widely debated in military and civilian circles. The cost was one issue: a projected billion dollars or so. Some doubted that the scheme would work, or that it could prevent a nuclear war even if it did. Still others, thinking back a dozen years to France in World War II, feared a “Maginot Line mentality,” in which a defensive barrier would yield a false sense of impregnability. In the end, whatever its imperfections, the benefits of such a radar fence made it indispensable as part of a revamped air-defense system, which would also include improved surveillance on the ground and in the air, advanced communications and computing facilities, and a centralized staff to put all the information together.