Continental Air Defense- The DEW Line

Successful air defense requires three elements- early warning, control measures, and the interceptors. This post deals with the first of these three elements.

The title of this post is something of misnomer, as the DEW Line was but one component of the network of detection and early warning systems the Air Force fielded to defeat any Soviet bomber attack on North America.

During World War II, the US had built a respectable network of radar posts along both the eastern and western seaboards. As the threat of Soviet bombers began to appear in the post war era, the radar “fence” was modernized.  But the high speeds of post-war aircraft meant that radars based solely in the US would not provide enough reaction time for successful intercept short of the bombers targets.

The first step was the Pinetree Line. In cooperation with Canada*, a string of radar installations was built across southern Canada to provide early warning. But the Pinetree line still didn’t provide enough strategic depth. The Mid Canada line was added, along roughly the 54th Parallel. Still, not enough. Accordingly, in 1954, Canada and the US signed an agreement to construct the most northern possible line, along the 69th Parallel. This put the Distant Early Warning Line (DEW Line) about 200 miles inside the Arctic Circle. It stretched from Alaska, across the northern reaches of Canada and all even included stations in northern Greenland.


It was a massive engineering project. The US and Canada had to build the infrastructure just to built the infrastructure for the installations. That is, there were no roads, ports or airfields in the region to ship materials to. Once that was done, contractors still faced the challenge of building installations that would have to be entirely self sustaining for months at a time. And short of working iin space, there are few environments harder to build stuff in than the Arctic. The extreme cold and high winds dictated much of how the stations were designed. Stations were prefabricated on either the east or west coast of Canada, and the components were then moved into position, often being dragged on sleds for hundreds of miles. By mid 1957 less than two and a half years after starting,  the project was complete.

The DEW Line used three types of installations. The main, nodal type had a long range search radar, housing for the operators, maintenance personnel, and support staff such as cooks, barracks  and some very modest recreational facilities. The second type had the long range radar, but only had a small skeleton crew of operators. The third type used a short range radar to cover gaps in the main belt of coverage. These were unmanned, and transmitted their information to the nodal units. The DEW Line was a cooperative effort with Canada. While the system was paid for and contracted by the US, Canadian labor actually did much of the work. Main nodal stations were operated by US Air Force personnel, while the secondary stations normally had Canadian personnel. Each installation flew both the American and Canadian flags.


After detecting any intrusion, the next problem was getting that information out. Remember, they couldn’t just pick up the phone. There were no phones there. Remember, the area up there had nothing in the way of development. And satellite communications didn’t exist. Heck, the first satellite wouldn’t be launched until about the time the DEW Line was completed. The primary communications link was a tropospheric scatter radio system. That is, to overcome the line-of-sight limitation of radio, they would bounce radio waves of the troposphere to a receiving station. Anyone who’s picked up an AM station from a thousand miles away at night can understand the concept. Source materials are unclear if the tropo scatter was primarily voice communications, or as I suspect, the raw video of the radar returns was also transmitted to the receiving stations.

Now, smart readers like you will look at the map above and say, “XBrad, what’s to stop the Soviets from just flying down the east or west coast and bypassing the DEW Line?” Well, a couple of things. First, the limited range of any bombers meant they’d have to take the shortest possible route to reach certain targets. Secondly, the US had also taken steps to keep the Soviets from doing just that.

The DEW Line was the most visible effort to build a radar fence to guard the US. Three other programs were also used, two very successfully, and one with only limited success.

The failed program was the Texas Towers. Texas Towers were in effect a DEW Line type station on the top of an oil rig platform. Offshore oil rigs were still a new concept in those days.  Originally, the Air Force planned to operate five TT’s mounted on shallow banks off the eastern seaboard. In the event, only three were built.

Texas Tower 2

Texas Tower. Note FS/AKL class ship resupplying the platform.

Tower Four was destroyed in a hurricane in 1961, with the loss of 28 lives. Between the risks, and the towers lack of detection capability against ICBMs and sub launched missiles, the decision was made to decommission them in 1963.

The Navy had hundreds of destroyer escorts from World War II that were two slow to truly be effective against submarines. But they were relatively young ships, and the diesel powered ships had astounding endurance. By mounting additional long range air surveillance radars, they served yeoman duty as radar pickets along both seaboards. They could remain on station for long periods of time, had significant self defense capability, decent air search capability, and were better able to withstand adverse weather. Further, they could be repositioned as needed to beef up coverage in weak areas.

The last element was airborne coverage. Generally, the detection range of a radar is determined by two things. The height of the radar, and the altitude of the target. Surface mounted radars can detect high flying aircraft 200 to 300 miles away. But against low flying aircraft, their range is greatly decreased. The curvature of the earth means the line-of-sight radar waves just can’t reach low flying aircraft any further. But by mounting a search radar aboard an aircraft largely overcomes this obstacle. So that’s just what the Air Force (and Navy) did. The Navy actually started experimenting with Airborne Early Warning (AEW) radar during WWII, using modified B-17s and TBM Avengers.** For this Cold War mission, Lockheed Constellations were used. The EC-121 Warning Star  mounted a large search radar in a belly radome and a height finding radar in a fin like radome atop the fuselage. Several Warning Stars would patrol well offshore of each seaboard.

Between the DEW Line, the other radar picket lines in Canada, Navy picket radar ships, and the Warning Star patrols,  any Soviet bomber attack would almost certainly be detected, and far enough out to mount a strong defense.

Just as this multilayered detection network became operational, the Soviet ballistic missile threat came onto the scene. This network was not suitable for missile detection. The BMEWS system is beyond the scope of this series. But the threat of Soviet bomber strikes was still significant enough that large portions of the network remained in use well into the missile age, and the DEW Line itself was operated until the early 1980’s when the radars were replaced by a smaller network of modern radars. The new network, the Northern Warning System, was transferred to Canadian control in the mid 1980s and serves to this day.

Next, we’ll look at how the information gathered by this network was used to control the defense.

*Since the 1950s, continental air defense has been just that, the defense of the entire North American continent. The current command, NORAD, is a joint US/Canadian force. The commander of NORAD is always a US officer, and his deputy is always a Canadian officer. The radar systems, ground control systems, and very often the fighter aircraft have been identical. The Canadians have long had an extremely robust capability for air defense. Their current capability, in terms of numbers, is pretty thin, but their knowledge and dedication to the mission has been at least good as our own for many a year. Throughout the Cold War, Americans slept secure in their beds while their northern neighbors guarded the night skies.

**Steeljaw Scribe has an excellent series on the development of Navy Airborne Early Warning. 

4 thoughts on “Continental Air Defense- The DEW Line”

  1. There were still a few of those DERs around when I joined in ’72. The north Pacific was a regular station for them for awhile. They also got detailed to Operation Market Time in Vietnam (if you’ve read the “Arnheiter Affair” you’ve read about a Vietnam tasked DER). The DERs were the last of the Diesel DEs.

    On the east coast, the NORAD was forced to rely on a net of FAA radars combined with military radars. It was very unlikely Ivan was coming from that direction anyway. The AF was able to set up a good array of long distance radar sites along the Cascades by the early 60s. My father was stationed at Adair AFS near Corvallis, OR from ’61-’66. The “Block House” was built as a signal processing station for a goodly chunk of the radars in Oregon and was linked to bases at ADC Portland and Klamath Falls where the AC were actually based (Adair AFS did not have a runway. You can still see almost the entire infrastructure as I remember it if you look on Google Earth a bit north of Corvallis. It’s known as Adair Village).

  2. You mention the DEs the navy converted to DER (Destroyer Escort – Radar). There were also a dozen DDR conversions of the Gearing-class, but clearly this class’s capability allowed it to also perform the old radar picket duty for the fleet. Sixteen Liberty ships became YAGR with the same mission. There was a project to convert old escort carriers to the task (with an active air wing), or setup old Victory ships with radar and SAM batteries. A few World War II fleet submarines received the elaborate radar sets and became SSRs. But the ultimate Navy radar picket was the SSRN-586 Triton. While designed to support the fleet, the Triton’s systems were supposedly able to integrate into the larger air defense network.

    1. As you note, most non-DER platforms were designed to operate with the fleet.

      In fact, DERs were initially designed to support fleet operations, mostly because there were a lot of them available, and they were too slow to really provide protection against modern subs. But that same lack of speed limited their usefulness in supporting the fleet. Adding them to the continental air defense mission was almost something of an afterthought. The capability was there, why not use it?

      The Gearing DDRs were able to keep up with the fleet. Further, their steam plant had a much shorter endurance than the diesel DERs, making them less suitable for the role of continental defense. I’ve seen endurance figures of about 12,000nm for the diesels. You can stay on station a loooong time with that kind of endurance.

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