Practice Nine

On the 2nd of March 1965 the US opened Operation Rolling Thunder. This was the tightly controlled bombing of North Vietnam in an attempt to pressure the communists into halting their insurrection in the south. The target selection was controlled by the White House, and missions were done with very limited rules of engagement. So much so that pilots complained they needed a lawyer in the rear seat to tell them what they could do. A year later the operation had resulted in no movement from the North Vietnamese, and the US Secretary of Defence, Robert McNamara, was unhappy and looking for new ideas. That’s when Professor Roger Fisher, a lawyer and government consultant, suggested something akin to the Korean DMZ. A band of minefields, bunkers and clear vegetation stretching across Vietnam. 

 Such an installation would require barbed wire, minefields, multiple firebases and mass defoliation along its 160-mile length. McNamara approached the armed forces, who were uniformly aghast at the idea. They estimated it would take seven full divisions, and four years to complete. Despite this McNamara commissioned a study by a group of scientists. They concluded that it was feasible to emplace something, albeit by using aircraft. The study included several ideas on employing electronic equipment to detect the passage of the enemy, which could then be responded to, rather than a traditional blocking force. Equally, the Ho Chi Minh trail proved problematic as it wound through Laos. And like the Maginot line before, and fortification could simply be driven around. 

Example of a Vietnam Firebase. These would need to be dotted across the width of South Vietnam.

 

Despite all this work was begun. The development team was given top priority, and an unlimited budget. The entire project was codenamed Practice Nine and would cost an estimated $1 billion. The project was further broken down into three subgroups. The physical component in Vietnam would be codenamed Dye Marker, while the electronic component in Laos became Muscle Shoals. Finally, the technology to implement the project was code named Igloo White.

There were, of course, the usual plethora of crazy ideas suggested, and rejected. Two choice ones of these were a combination of the Second World War Pigeon and Bat bombs. It was suggested that pigeons could be fitted with explosive vest, and trained to land on the top of trucks, at which point the bombs would detonate. This, of course raises the age-old question of ‘What is the laden weight of a pigeon?’ Well, it is apparently about 10% of the body mass, or about 30-grams. One wonders how effective a 30-gram bomb would be, considering you would also need a detonation mechanism. In the end the scientists raised another objection, how to train the pigeons to land on only communist trucks. Another idea was to use sensors shaped like dog defecation. However, it was quickly pointed out that the area of the Ho Chi Minh trail had no native canine species. 

Marines at Khe Sanh

 

Dye Marker began construction in 1967 in Quang Tri Province. Things went badly as most of the supplies for it were diverted to Khe Sanh for the defence of that location. When that battle was over work never resumed on it. However, Muscle Shoals was vastly more successful. 

One of the assorted sensors being dropped by a USAF bomber.

 

The technology used in Laos consisted of several types of air droppable sensors, with batteries and transmitters. Around 20,000 would be dropped in strings of five to six to ensure that some of the sensors would survive. They came in several forms. One chemically detected human sweat and urine. Another based upon the standard US sonar buoy contained microphones, and the camouflaged parachute would catch in the trees allowing it to hang and listen. There was also an acoustic sensor that stuck into the ground, with an antenna that was camouflaged to look like reeds. Finally, there was the ADSID (Air-Delivered Seismic Intrusion Detector). This lodged itself in the ground and picked up vibrations. 

Inserting an ADSID by helicopter.

 

The data gathered was then transmitted by the sensor’s onboard radio. However, there were no modern data handling devices that we currently have. Equally, range on the radios was limited. Thus, the USAF had to mount a continuous standing watch. For the first few years this was done by a modified Lockheed Constellation airliner with a designation of EC-121R. These would loiter for eight hours apiece, 24 hours per day, over the area’s seeded with sensors. 

EC-121R

They would pick up the transmissions from the sensors and transmit them back to the base, where the data was fed into two IBM 360-65 computers. The data on troop movements was able to be assessed in real time. From that targets could be identified, and strike missions tasked to aircraft loitering in the area. Equally, fresh infiltration routes could be detected, and movements monitored. Locations such as overnight stops, repair points and other fixed locations could be targeted at a later date. 

 The technology had some limitations. One major problem for the acoustic sensors was actually a local frog whose loud croak cause issues with the microphones. The North Vietnamese rapidly became aware of the sensors and took counter measures such as hanging buckets of urine on trees to fool the chemical sniffers. Equally, the coverage of the sensors was not universal. The Ho Chi Minh trail is not a single track but many thousands of routes. An example of this is the appearance of communist tanks in South Vietnam in 1972. Some of these had come down the Ho Chi Minh trail, and not one of the sensors had picked them up. 

QU-22B

As Muscle Shoals proved its worth an experiment to use a QU-22B Pave Eagle to collect and re-transmit the data was trialled. The EC-121R’s had crews of around eighteen. The QU-22B only had a single pilot and were single engine craft. As this was a success the EC-121R’s were shutdown. During that time there are many recordings, including ones of convoy’s getting hit by airstrikes. Another has a road clearing crew chopping a tree down, only for the tree to fall on one of the workers. In yet another one an NVA soldier climbs up a tree. He can see the parachute that inserted the sensor. He is overheard to explain to his colleagues he wanted to retrieve the cloth and send it to his girlfriend so she could make a dress.  

The Muscle Shoals program would run until 1972. But there is considerable argument over how effective it was. It is pointed out that the USAF claimed more trucks destroyed than intelligence said were in North Vietnam at the time. The truth is likely between the two, as the USAF was probably over-claiming, while intelligence was under reporting. A factor for the USAF over claim was although they could get real time locations, these were not pinpoint accurate, so they had to work on principle of smashing the area where the trucks were reported, and such a haphazard way of attacking leads to some over estimation.

Ultimately this focus on number of trucks destroyed sounds very similar to the fixation with body counts from the ground forces and is not how you win a war. 

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Image Credits:

defense.gov and thefutureofthings.com