The Introduction of the AGM-45 Shrike

Takhli Air Base in Thailand, Spring 1967: F-105D and F-105F Thunderchiefs taxi out, armed with AGM-45 Shrike ARMs.

A secret program call The Wild Weasel, intended to counter surface to air missiles, had been deemed a success, but its fate was still uncertain. Two problems continued to plague the fledgling project. One was the speed of its aircraft, F-100 Super Sabres. They were much slower than the F-105 Thunderchiefs they were supposed to protect. This forced the F-105s to fly at much slower speeds on approach to the target area, posing unnecessary risks to the strike pilots. This also meant that the slower Weasels were often left to fend for themselves, on the way in and out of the target area.

Danger to Crews and Aircraft Motivates Change

As Weasel aircraft left the target area, the crew would notice that they had been left alone, as the F-105s disappeared in the distance, heading south. This was where the motto "First in, Last out" originated.

The Weasel’s ordnance load was another problem: They just couldn’t carry as much as the F-105s. While both carried 20 millimeter rounds and rockets, the F-105s also carried conventional bombs. Also, to destroy the targets with their particular payload, the Weasels had to head straight into the surface-to-air missile (SAM) site at an extremely low altitude. This put airmen well within the range of anti-aircraft artillery and even created risk from small arms fire.

In March of 1966, the danger became a reality: A second Wild Weasel crew was downed, and both men killed, when their plane was struck from below. The loss motivated development of new ordnance configurations.

Cluster bomb units proved to be among the most promising for suppressing anti-aircraft fire and triggering explosions in the missiles. Each bomblet detonated just above the ground, sending thousands of steel pellets throughout the site. In addition to conventional bombs carried by the F-105s, the Weasels also tried dropping napalm canisters. However, the large tanks required a low release altitude and created considerable drag on the already slow F-100 aircraft.

The AGM-45 Shrike Anti-Radiation Missile

In March 1966, the Air Force found a solution: They replaced the plane. A new version of the F-105F would take over the Weasel mission, and it would carry a new type of missile: The radar-seeking AGM-45 Shrike. The North Vietnamese had been supplied with Soviet SA-2 Guideline SAMs, which were guided to their target by Fan Song trailer-mounted fire control and tracking radars. The Shrike worked by locking on to emissions coming from the radar van, then following them back to the source.

Development of the Shrike had begun back in 1958, to counter the emerging threat posed by the Soviet SA-2 surface-to-air missiles. Impetus was given to the effort when a United States U-2 reconnaissance plane was shot down over the USSR in 1960, by an SA-2. Another U-2 spy plane had been downed by an SA-2 over Cuba during the Cuban Missile Crisis of October 1962. As the U.S. air war over North Vietnam grew in scope, development of an answer to the SA-2 threat was nearing completion.

The arrival of the specially configured, two seat F-105Fs finally provided the Weasels with the speed needed to keep pace with U.S. strike aircraft and to evade enemy threats when necessary. However, it was the arrival of the Shrikes, which first saw action in April 1966, that had the biggest impact on the Weasel’s ability to suppress SAMs. Aircrews noticed a big change in the behavior of North Vietnamese radar operators and their Russian advisers. When Shrike missiles were launched, the Fan Song radars sometimes went down, leaving the American anti-radiation missiles without a signal to guide them to their target. With their radars went down, the North Vietnamese were left without the ability to accurately target U.S. aircraft.

Deadly Attraction: Closing in on Your Mortal Enemy

While the Shrike ARM increased Air Force stand-off weapons delivery capability, solving problems associated with having to overfly SAM sites in order to take them out, it had its limitations. Although its theoretical maximum range was around seventeen miles, the range from which it could practically be fired was only around 12 miles. If fired from greater ranges, SA-2 crews could launch a surface-to-air missile, guide it to intercept the American warplane, then shut down their radar before the AGM-45 could hit the SAM site. This was a product of the SA-2's speed advantage: The SA-2 Guideline could travel at Mach 3.5 while the tortoise-like Shrike could only reach Mach 2.0.

To avoid giving enemy radar operators a chance to shut down before getting blasted, the Wild Weasels had to launch from a within a range where the Shrike's flight-time would be less than the time of flight of the SA-2. That calculation limited the Shrike to a maximum effective range of ten to twelve miles. Additionally, its rather small 145 pound high-explosive warhead would do comparatively little damage, even when the target was accurately struck.