How the U.S. Military Went to War against Vietnam's Radar and Air Defenses

How the U.S. Military Went to War against Vietnam's Radar and Air Defenses

Hanoi had top of the line weapons to kill U.S. fighters and bombers. Here's how Washington punched back. 

Captain John E. Donovan, an electronic warfare officer, monitored the equipment in his F-100F Super Sabre fighter. It was December 22, 1965, and his plane was part of a strike mission searching out enemy antiaircraft sites. Two days earlier, a similar mission had gone badly, resulting in the loss of a plane and its crew. As the F-100F in which he was flying raced through the skies over North Vietnam, Donovan detected a signal from enemy radar known as a Fan Song. He notified the pilot, Captain Allen T. Lamb, who began maneuvering the plane to help locate the radar. Lamb took the plane down until the signal disappeared and then ascended until they picked it up again, using the mountains and valleys to help them avoid becoming a target themselves. The two men were flying over the southwestern section of the Red River Valley, which was situated northwest of Hanoi.

Streaking around a hill, Lamb took the F-100F up to 4,500 feet and began looking for the radar and its attendant SA-2 surface-to-air missiles (SAMs). He saw the SAM deployed in the middle of what looked like a village. He noted the tips of three missiles bristling out from beneath a thatched hut, which afforded the missile battery good camouflage. Wasting no time, Lamb radioed the accompanying F-105D Thunderchief fighter bombers to follow his lead. The F-100 swooped down on the enemy position and fired rockets to mark the target for the bombing runs. The F-105 strike succeeded in knocking out the battery. Debris from the destroyed SAM site flew 400 feet into the air amid a column of smoke.

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The American aviators had little time to enjoy their triumph. Donovan detected another Fan Song radar. He could tell this one was already well into its attack cycle, detecting what was known as a high-pulse repetition frequency. This meant that the enemy was only about 30 seconds from launching. The operator would double the frequency at this point to provide a sharper radar image. The entire flight turned back toward its base in Thailand, dropping to low altitude to avoid the Fan Song. One victory was enough for the day. The team had successfully proven a new concept of air warfare designed specifically to target the radars that were vital for modern guided missiles to track their targets. The concept, which was code-named Wild Weasel, was coming of age.

As air warfare evolved during the latter half of the 20th century, aircraft had more to worry about than just enemy cannons and machine guns. Advances in rocketry led to powerful new antiaircraft missiles, and developments in electronics greatly increased the capability of radar and guidance systems. The antiaircraft missiles of the World War II-era could barely be counted on to strike a large area target, but by the 1960s much smaller versions could track aircraft in the sky. The pace of progress was accelerating and air forces around the world struggled to counter each new improvement.

In the first months of the Second Indochina War, commonly known as the Vietnam War, American aircraft began to suffer losses from North Vietnamese SAMs, which were supplied by the Soviet Union. The SAMs covered medium-to-high altitudes, up to 60,000 feet in the case of the SA-2. When U.S. aircraft came in at low altitude to avoid the missiles, they were vulnerable to traditional antiaircraft fire. To counter this threat, the U.S. Air Force initiated a program called Wild Weasel. The program became so successful that the name has since been applied to every U.S. Air Force aircraft developed for this sort of mission.

The mission of a Wild Weasel aircraft is to locate enemy antiaircraft radar and either destroy it or target it for attack by other aircraft, usually accompanying ground attack planes. Radar systems send out waves of energy that reflect off targets, such as aircraft, and return to the radar device, allowing radar operators to track and target the aircraft. But these waves can themselves be detected and tracked back to their source, revealing the position of the radar and allowing the hunted to become the hunters. Accomplishing this task requires specialized equipment and weapons not carried by regular aircraft.

The U.S. Air Force began the Wild Weasel program in October 1965, just a few month after the North Vietnamese SAMs, crewed largely by Soviet advisers, began taking their toll of American planes. By early November the basic equipment had been tested and field testing began. Electronic Warfare Officers (EWOs) learned how to operate the electronics and read the displays that would lead them to enemy radar. Those radars not only had to turn on to lock onto a target, but also had to stay on long enough to track it and then home in on it. The test missions were flown against American radar systems that were similar to the Fan Song. EWOs learned that their equipment worked best at medium altitudes flying directly toward the radar beam’s point of origin. Results were poor when flying at low altitude or parallel to the source.