Six Linguists Hunted Nuclear Threats 5 Kilometers From the Front
By Miriam Adler ·
Friendly units faced potential nuclear or chemical surprise attacks because an inefficient reporting system forced crews to bypass protocol for urgent warnings.
A ballistically protected S-661 shelter, mounted on an M923A2 5-ton carrier, is not designed for comfort. It is designed to survive small arms fire while its occupants listen to the air. Inside this shelter, a crew of six linguists operates the AN/TSQ-138 Trailblazer, a mobile ground-based electronic warfare signals intelligence (EW/SIGINT) intercept system. According to a program page mirrored by the FAS Intelligence Resource Program, the system was fielded in Army Communications, Electronic Warfare, and Intelligence (CEWI) battalions in the late 1980s.
The Trailblazer is a tool for the tactical commander, a way to strip the veil of secrecy from the enemy's communications. It searches for, intercepts, records, and identifies radio signals across the HF, VHF, and UHF frequency ranges. To function, it requires a 30 kilowatt generator housed in a towed trailer support unit and a quick-erecting telescopic mast for its direction finding (DF) antenna group. It is an apparatus of precise, cold geography, relying entirely on line-of-sight (LOS) to translate invisible waves into actionable intelligence.
6 x 98G (Linguists)
The technical specifications of the AN/TSQ-138 focus heavily on frequencies and power sources, but the human cost of the operation is found in the crew requirement: "6 x 98G (Linguists)." These individuals are the organic processors of the machine. They do not merely operate a dial; they translate the intent, the fear, and the orders of an opposing force in real-time.
The FAS mirror notes that the system was subject to "multiple and substantial product improvements" throughout the 1980s. This suggests a desperate, iterative scramble to keep pace with a "rapidly changing threat environment." For the linguists inside the ballistic shelter, this evolution meant the difference between identifying a target and being blind to a shift in the enemy's electronic signature. They were the bridge between the raw signal and the commander's map, tasked with the delicate work of direction finding in the VHF band to determine exactly where a signal emitter was located.
Document imagery from irp.fas.org From the files: irp.fas.org
5 to 15 Kilometers from the FLOT
The deployment of the Trailblazer is not random; it is a choreographed geometry. The record describes a "Lazy W" formation, with three to five systems positioned 5 to 15 kilometers from the FLOT—the Front Line of Own Troops. This positioning is a calculated risk. The crews are close enough to the enemy to maintain the necessary line-of-sight for effective monitoring, yet far enough back to avoid immediate overrun, provided their ballistic protection holds.
However, the environment itself is an adversary. The effectiveness of the Trailblazer is fragile, easily compromised by the physical world. The record lists several obstacles that can interfere with antenna emplacement or signal reception: power lines, pine trees, and the requirement for "30 feet (10 meters) clear to the left." Even the landscape of war disrupts the intelligence flow. The FAS entry specifies that "barbed wire, armored vehicles, surrounding hills, trees, and streams" can affect signal reception. Most pointedly, any metallic bodies located near a set—including "RADAR scattering camouflage"—can produce DF inaccuracies. The very tools used to hide from the enemy can blinker the eyes of the interceptor.
Document imagery from irp.fas.org From the files: irp.fas.org
NBC and the VHF Radio
Intelligence is only as useful as the speed at which it can be delivered. For the Trailblazer, the standard method of reporting is the UHF net radio protocol (NRP). The record is blunt about the failings of this system, describing it as "a rather slow and inefficient system."\ In the context of a tactical battlefield, slowness is a liability that can be measured in casualties.
Because of this inefficiency, the military established a bypass for what they termed "extremely perishable" reports. If the linguists intercepted intelligence involving a "possible surprise on a friendly unit or use of NBC by the enemy," they were instructed to ignore the standard protocol and report immediately to the Platoon Leader over VHF radio.
The mention of NBC—nuclear, biological, and chemical weapons—shifts the nature of the Trailblazer from a tactical intercept tool to a desperate early-warning system. In those moments, the "slow and inefficient" bureaucracy of the UHF net was discarded in favor of the raw urgency of the VHF link. The linguists were not just tracking movements; they were listening for the heralds of mass casualty events.
While the Trailblazer could interoperate with the airborne QUICKFIX system and other platforms, its fundamental nature remained grounded and precarious. The FAS record ends with a mention of the "Basis of Issue Plan," noting that five Trailblazer systems were authorized for assignment to each heavy division. It leaves us to wonder how many of these "Lazy W" formations were actually deployed in the final years of the Cold War, and how often the linguists heard something that the "inefficient" reporting systems could not convey in time.