Igloo White was rushed into service during the Battle of Khe Sanh and successfully passed its first operational test. Combined with Operation Commando Hunt in 1969, the system served as the keystone of the U.S. aerial interdiction effort of the Vietnam Conflict.
Costing between $1 and $1.7 billion dollars to design and build (and another billion dollars per year to operate over the five-year life of the operation) and possessing and controlling some of the most sophisticated technology in the Southeast Asia theater, the effectiveness of Igloo White still remains in question.
After the initiation of the strategic aerial bombardment of North Vietnam (Operation Rolling Thunder) in March 1965, Washington saw that program as its chief method of relaying signals to Hanoi to cease its support of the southern insurgency. When that failed as a strategy, the aerial effort was redirected to serve as an anti-infiltration campaign. After a million sorties were flown and more than three-quarters of a million tons of bombs were dropped, Rolling Thunder came to an end at the direction of President Lyndon B. Johnson on 11 November 1968.
As early as 1966 Secretary of Defense Robert S. McNamara had become disenchanted with Rolling Thunder. In January McNamara was presented with a working paper by the American academic Roger Fisher, who proposed a less costly physical and electronic barrier that would be located in South Vietnam. It was to consist of a 216-mile long, 500 yard-wide barrier that would stretch from the South China Sea south of the Demilitarized Zone (DMZ), across the Laotian frontier and on to the border of Thailand. The physical barrier itself would be supported by electronic sensors and extensive minefields. Fisher estimated that it would take approximately five U.S. divisions to erect and defend the system.
The Joint Chiefs and CINCPAC turned down the concept, believing that it would consume the efforts of too many troops and create a logistical nightmare. McNamara, however, was intrigued. Ignoring the military chiefs, he approached the Institute for Defense Analysis and requested that it fund an study of the concept. The project was then handed over to the Jason Division (also referred to as the Jason Group or Jason Committee), a group of 47 scientists who were to study and develop the technology necessary to make the physical/electronic barrier feasible. The group concentrated its efforts in three key areas: communications; data processing and display; and sensor development. On 15 September 1966, McNamara made Army General Alfred D. Starbird the head of the newly-formed Defense Communications Planning Group (DCPG), which was to oversee the implementation of the program. The barrier concept was then given the designation Practice Nine. The DCPG’s original mission profile, as of September 1966, was simply to implement the anti-infiltration system devised by the Jason Division. The original plan foresaw the deployment of both a physical barrier in addition to an air-supported barrier using various electronic sensors.
In June 1967 the barrier project, by then referred to as the Strong Point Obstacle System (or SPOS) was renamed Illinois City, which lasted for a month before the program was redesignated Dyemarker. On 6 July, groundbreaking ceremonies were conducted for the command center of the operation. Construction work was completed three months later. The new Infiltration Surveillance Center (ISC) was located at Nakhon Phanom, Thailand, nine miles west of Nakhon Phanom city on the banks of the Mekong River. The first commander of the unit was Air Force Brigadier General William P. McBride, whose superior was the deputy commander of the Seventh/Thirteenth Air Force at Udon Thani, Thailand. From its creation the ISC (and the operations conducted from it) was known as Task Force Alpha.
On 8 September 1967, the electronic portion of Dyemarker was divided and the aerial, sensor-based portion was designated Muscle Shoals. On 1 June 1968, the aerial portion was redesignated Igloo White. That name became the most associated with the program though various elements received a number of separate codenames. All resources for Dyemarker/Muscle Shoals were redesignated Duck Blind in April 1968, and in June 1968 Muscle Shoals outright became Duel Blade. In October 1968 Duck Blind was changed to Duffel Bag.
In mid 1968, the physical barrier concept was pushed aside after the North Vietnamese overrun of the Lang Vei special forces camp and the siege of Khe Sanh. The barrier concept was reduced to an aerial, sensor-based electronic interdiction program that was to be conducted in Laos.
The first sensors utilized by the program were Air-Delivered Seismic Intrusion Detector (ADSID), which had been developed from devices then in use in underground mapping for the oil industry. The device could sense vertical earth motion by the use of an internal geophone and could determine whether a man or a vehicle was in motion at a range of 33 and 109 yards respectively. The first acoustic sensors were developed from the U.S. Navy's Project Jezebel anti-submarine warfare sonobuoys, which recorded and processed sound by the utilization of an audio spectrum analyzer. The first model of seismic detectors (Phase I) outshone their contemporary acoustic types in the quality and quantity of the information they reported. The Phase I models of both the acoustic and seismic sensors were only available for operation in a continuous mode, which meant that under normal conditions, their lithium batteries would function for approximately 30 days.
The Acoustic Seismic Intrusion Detector (ACOUSID), combined the operations of both seismic and acoustic devices, with the added ability to transmit sound from a built-in microphone. The ACOUSID had three switchable detection modes: in the C mode, a line spectrum detector determined the presence of enemy vehicles and had an effective range of 1,094 yards; an I Mode which was activated by sounds picked up by its internal microphone and could detect personnel at a range of 438 yards; and a B Mode that combined both of the above abilities and operated in a continuous real-time mode of 40 activations per hour with a battery life of 30 days.
The sensors reported their data via radio frequency channels ranging upward from 162.5 megahertz (MHz) to 133.5 MHz on the very high frequency band. 31 channels were assigned to each type of sensor with a 375 kHz separation between each channel. Every channel contained 27 identification codes or addresses which could be set in the field prior to emplacement. Thus, a total of 837 individual sensors (27x31) could be deployed at any one time without signal duplication in a single operational zone.
The deployment of Gravel mines and the Wide-Area Anti-Personnel Mine System became integral parts of the operation. Other weapons were specifically developed or otherwise became associated with the campaign as well. These notably included the BLU-31/B and Mk 36 air-dropped mines, BLU-43/B and BLU-44/B landmine system (Dragontooth), the BLU-72/B fuel-air explosive (Pave Pat), and the BLU-52/A chemical bomb (filled with bulk CS-2 powder). Anti-vehicle operations in support of Muscle Shoals/Igloo White were designated Mud River, while anti-personnel operations received the codename Dump Truck.
PAVN personnel moving on foot through the trail system would be detected by the detonation of air-sown, aspirin-sized, wide-area Gravel mines, which would activate the sensors. Subsequent Bomb damage assessment missions and hand emplacement of sensors and mines in support of Muscle Shoals would be carried out by the reconnaissance teams of the highly-classified Military Assistance Command, Vietnam Studies and Observations Group (SOG). A number of hand emplaced units were developed for this role, including the MICROSID and MINISID, and a device designed to work with either called MAGID, a magnetic detector, designed to be triggered by amounts of metal as small as an infantry rifle.
The sensors were designed for air deployment by either of two means. The first was by parachute, which would hang the devices in trees, where they appeared to be part of the foliage. The second method was the use of gravity, which would drive the spike-shaped device into the ground like a lawn dart, burying all but their antennae, which were designed to appear as weeds. Surprisingly, approximately 80 percent of the air-dropped sensors were found to be operational after delivery.
The second phase of sensor development improved the older models by providing for non-continuous operation as directed by the ISC. They also had the capability of carrying out three separate reporting functions: to report current information (transmitting noises or earth tremors); to keep silent, but to count impulses and respond when queried; or to remain in constant operation like the Phase I models. Their batteries also provided the ability to operate for approximately 15 days longer than the Phase I models (45 days).
During late 1969, Phase IV sensors began to be deployed in-theater. These had a greater number of available communications channels, which allowed the seeding of a larger sensor field without fear of signal interference. By 1971–1972 a new sensor with a commandable microphone (COMMMIKE III) and another with a vehicle ignition detector (EDET III, which could detect the unshielded ignition systems of gasoline engines) were introduced. The sensors were not cheap. In 1972 U.S. dollars the ADSID cost $619.00, the ACOUSID $1,452.00, and the engine detector $2,997.00. During the life of the operation approximately 20,000 sensors were deployed in Laos.
The sensor transmitters would relay their data to the second element of the system, an orbiting EC-121R aircraft of the Air Force's 553rd Reconnaissance Wing, based at Korat Royal Thai Air Force Base. The EC-121s would then relay the collected information to Nakhon Phanom. At Task Force Alpha, the last of the three components in the system, the intelligence data (from a variety of sources, not just the sensors) would be entered, collated, retrieved, and stored by two IBM 360/40 (later two 360/65) computers. Technicians at the center controlled the system from a variety of video displays that were also linked to the computers.
Analysts at the 200,000 square-foot center concentrated on such arcane topics as pathway predictions, delay intervals, route segments, and choke points. The computers analyzed sensor data and compiled intelligence information and then made predictions as to where and when a particular PAVN truck convoy would be geographically located. According to author John Prados, the system functioned "exactly like a pinball machine... in truth, the mavens of the electronic battlefield became pinball wizards".
The effectiveness of the system was determined not by how long a sensor would last in the field, but by the adequacy of coverage by a particular string of sensors. For instance, a well placed string with several failed sensors was more effective than a fully functional string placed in the wrong location. The electronic data was, however, only as good as the human analysts and operators at the ISC. The knack of timely sensor activation depended on careful study of device locations and the patterns of PAVN logistical behavior.
The sensors were delivered to the target areas by U.S. Navy OP-2 Neptunes of VO-67 or by U.S. Air Force helicopters, both based at Nakhon Phanom. Due to increasing PAVN anti-aircraft artillery defences encountered in southeastern Laos, delivery in high-risk areas of the trail system was handed over from the Neptunes to Air Force F-4 Phantom II fighter-bombers that had been specially equipped for the missions.
U.S. strike aircraft were directed to predicted target areas by a variety of means. The first was for the ISC to relay target information to an airborne battlefield command and control center (ABCCC), which then routed bombers to a forward air control aircraft (FAC). The FAC then led the strike to the target. During inclement weather or complete darkness, aircraft could still attack the trail by utilizing either MSQ-77 Combat Skyspot (a radar-directed system) or LORAN (a radio-directed navigational system).
As the program (and PAVN air defences) evolved, so did the relay aircraft. The EC-121Rs and their crews proved too vulnerable and were partly replaced in 1969 and 1970 by QU-22Bs (modified Beech A-36 Bonanzas) which were to be remotely piloted. The aircraft suffered from mechanical difficulties, however, and were never flown during an operational mission without a pilot. They were replaced by C-130B models in December 1971.
Although the Marine Direct Air Support Center was at first reluctant to trust the sensors (which in fact replaced ground patrolling), they were soon convinced of their utility. The Marines credited 40 percent of intelligence available to the Khe Sahn fire support coordination center to the sensors. General Westmoreland was ecstatic about Task Force Alpha's contribution to the victory at Khe Sanh. He had been one of the few high-ranking military officers that had supported the barrier concept since its planning stages.
With the conclusion of aerial operations around Khe Sanh and the close out of the Marine base, the focus of Igloo White (as the operation was redesignated in June) turned once again to Laos. On 15 November 1968, the Seventh/Thirteenth Air Force had inaugurated Operation Commando Hunt, a series of continuous interdiction operations against the Ho Chi Minh Trail that would continue until the end of American participation in the conflict. For the next four years Igloo White and Commando Hunt would be interlinked in the anti-infiltration effort.
With the advent of Igloo White/Commando Hunt, the aerial interdiction effort entered a new phase. Armed reconnaissance - the patrolling of known segments of the trail system by aircraft searching for targets of opportunity - gave way to strikes directed by the sensor system. That is not to say the Task Force Alpha had operational control of the aircraft that carried out the missions. The Seventh Air Force was not about to surrender the single air manager control that it had just fought so hard to obtain. Task Force Alpha supported the Seventh by gathering, analyzing, and disseminating intelligence. This intelligence was delivered from Nakhon Phanom to the Seventh's headquarters at Ton Son Nhut Air Base, where it issued the strike orders. The ABCCCs were also under the control of the Seventh, not Task Force Alpha.
The only exception to this arrangement was Operation Commando Bolt, a real-time, LORAN-based technique which utilized sensor strike zones derived from predicted target locations. These missions were coordinated by Task Force Alpha's Sycamore control center against targets that passed through strike modules (four strings of three to six sensors each). Air controllers at Sycamore then directly delivered the correct course, altitude, and speed necessary for the strike aircraft to deliver their ordnance to the correct coordinates.
There were some initial problems with the system. During Operation Commando Hunt I, for example, there were so many aircraft piling up in the air space over southern Laos that the air controllers and FACs could not keep track of them. Pilots, many of whom were veterans of Rolling Thunder, tended to arrive over the area in large waves instead of spacing out their arrivals over time. One technical failure, however, would have hugh ramifications for the entire program. The anti-personnel system, which was based on the dispersal of wide-area Gravel mines (the explosions of which would activate acoustic sensors) failed completely. The mines deteriorated too rapidly in the heat and humidity of Laos, thereby negating the system.
The North Vietnamese response to the threat posed by the sensors was swift. If PAVN troops could detect the general location of a sensor, they immediately began to search out others and destroy them. Another response was to simply avoid them. The final evolution of anti-sensor measures was to attempt to deceive them. The chief protection of the sensors proved to be the dense foliage that covered the majority of the logistical system, turning the enemy's chief protection against him. Doubtless, PAVN troops negated the effects of many sensors, but so many of them were sown over such a long period of time that the majority survived.
The 3rd Naval Construction Battalion designed fighting and living bunkers for the route, presenting them for tests and evaluation 1968, both in CONUS and in Vietnam. Also, 28 January 1968, COMUSMACV provided its own guidance for the planned creation of the ARVN Dyemarker Regiment. COMUSMACV envionsed a Regiment of 5 4-company Battalions and an Armored Cavalry Squadron. On 30 January, COMUSMACV informed the commander of III MAF of their proposed mission to augment the proposed ARVN force manning the barrier. The ARVN 2nd Regiment, of its 1st Infantry Division became earmarked for the barrier mission.
On 29 October 1968, work was stopped on the physical SPOS barrier, by that time redesignated as Duel Blade, under MACV Planning Directive 10-67, citing changes in the overall force posture, both enemy and friendly. The physical barrier would be replaced by the revised Duel Blade plan of active resistance utilizing air strikes, artillery and naval bombardment and mobile reaction forces. Base sites already constructed or under construction were to be used as support bases for the revised operation plan.
Though Igloo White’s primary focus was monitoring traffic along the Ho Chi Minh Trail, the DCPG's mission had been expanded to include sensors for a "wide range of tactical applications," as well as, a "Ground Tactical System" in 1968. The Ground Tactical System was envisioned as a tool for ground commanders in defending fire bases and other secured areas against attack, and was eventually employed around Khe Sanh. It was also noted that the US border patrol was testing the sensor equipment as a method of protecting US continental borders. Sensor equipment was deployed by July 1969 in South Vietnam for the purposes of countering boobytrapping and mining teams. A total of 56 sensors were diverted to the problem as a test, with testimony that vehicle losses were reduced by 50 percent in the first month.
Chief among the criticisms leveled against the system was its failure to detect the build-up to PAVN's 1972 Nguyen Hue Offensive. This cast doubt not only on the trustworthiness of the sensors, but on the adequacy of the entire system. The headquarters of the Pacific Air Force launched an investigation of the apparent failure and reported that "our estimates were in error." The report went on to state, however, that the lapse was not the result any failure of the sensors themselves, but the Air Force's false assumption that the trail net had adequate coverage.
The interdiction campaigns were also expensive. Igloo White cost around one billion dollars per year to operate. The cost of the bombing operations that the sensors supported amounted to approximately 18.2 million dollars per week. Those costs did not include the hundreds of aircraft lost during the interdiction campaigns or the priceless crews that manned them.
Scholars today remain divided on the merits of the electronic barrier system and the efficacy of the bombing campaigns that it directed. The claims of destruction made by the U.S. Air Force, both during and after the conflict, were originally taken as given. The only exception to this rule was at the CIA, which discounted Air Force claims at the time by as much as 75 percent. This was understandable due to the fact that the Vietnamese were basically silent during the 1970s and 1980s.
By the 1990s, new historical research (especially by Air Force historians Earl Tilford, Bernard Nalty, and Jacob Van Staaveren) and the publications of the Military Institute of Vietnam finally opened new perspectives on aerial interdiction during the Vietnam Conflict. During Commando Hunt for example, the Air Force claimed that 46,000 PAVN trucks had been destroyed or damaged by air strikes in Laos. These figures were hard to reconcile with the 6,000 trucks imported annually into North Vietnam between 1965 and 1970 — for all of its operations. American claims that 80 percent of the materiel that started down the trail was destroyed while enroute to the southern battlefields had to be altered in the face of loss claims of only 15 percent by the Vietnamese.
Thomas C. Thayer, chief of the Advanced Research Projects Agency for four years during the conflict, believed that only about one-twentieth of the cargo imported into the north moved southward on the Ho Chi Minh Trail and that more than two-thirds eventually reached the battlefields in the south. More recently however, a new study by Air Force historian Eduard Mark has attempted to rehabilitate the Air Force's original claims by finding a rough correlation between trucks imported into North Vietnam during the conflict and those that were claimed by the American pilots as destroyed. Only the opening of the Vietnamese archives to scholarly research will reveal the true effectiveness (or lack thereof) of the American electronic and aerial effort.
Published government documents