The Secret Sentry

by Matthew M. Aid

  As noted above, the Battle of Khe Sanh had commenced a week before the beginning of the Tet Offensive when the North Vietnamese 325C Division launched an unsuccessful three-battalion assault on marine defensive positions in the hills outside the firebase. Then for the next three weeks there was a surprising hiatus while the Communist Tet Offensive raged over the rest of South Vietnam. Newly declassified documents suggest that SIGINT played a major role in this delay. On the weekend before the Tet Offensive began, army and air force ARDF aircraft pinpointed the location just inside Laos of the NVA “Front” headquarters directing operations in the Khe Sanh area. On January 29, the day before the Tet Offensive began, forty-five B-52 bombers dumped 1,350 tons of bombs on the site of the North Vietnamese headquarters, and the radio transmissions that had been originating from the site disappeared for almost two weeks, indicating that the bombers had destroyed the enemy headquarters. 48

  It took the North Vietnamese several weeks to get reorganized. On February 7, NVA troops and tanks overran the nearby Green Beret base at Lang Vei. But rather than presage a massive assault on Khe Sanh, the attack on Lang Vei marked the beginning of almost three months of desultory North Vietnamese attacks on the firebase, which finally petered out in April. During this three-month period, the marines beat off repeated small-scale North Vietnamese ground assaults, in many cases, only after fierce hand-to-hand fighting, but no major attack on the firebase itself ever occurred. In fact, after the fall of Lang Vei evidence appearing in SIGINT indicated that the North Vietnamese had stripped troops from the front lines around Khe Sanh and sent them south. As a result, President Johnson and General Westmoreland’s fears that Khe Sanh would become the “American Dien Bien Phu” never materialized. The embarrassment felt by U.S. government and military officials in Washington and Saigon was palpable. The decisive battle with the best units in the NVA that they had hoped for never happened.

  According to a declassified NSA history, the Battle of Khe Sanh was “one of the greatest SIGINT success stories ever.” Much of the success can be credited to a tiny U.S. Marine Corps SIGINT detachment belonging to the First Radio Battalion and an attached South Vietnamese SIGINT unit, which had been operating a radio intercept site inside Khe Sanh since August 1967. Once the NVA attacks against Khe Sanh began, the marines started intercepting North Vietnamese artillery communications, which allowed the unit to warn the marine commander of the base every time the NVA planned to bombard the base. The marine SIGINTers also became expert in predicting when the North Vietnam -ese planned to attack the base. A declassified NSA document notes, “SIGINT predicted some 90 percent of all ground assaults during the siege.”49

  Throughout the battle, one or more army or air force ARDF aircraft continually orbited over Khe Sanh, pinpointing the sites of NVA radio transmissions, enabling the marines to direct air strikes and artillery fire toward the North Vietnamese commanders as they spoke on the radio. The process of locating NVA radio transmitters became so smooth that within ten minutes of a North Vietnamese radio operator going on the air, his location was being plastered by artillery fire or tons of bombs dropped by orbiting fighter-bombers.50

  The casualties that the North Vietnamese suffered thanks to SIGINT were considerable. Daniel Graham, then a colonel serving on the MACV intelligence staff in Saigon, said, “We knew . . . from intelligence that we had got our direction-finding equipment going so well up around Khe Sanh that whenever they’d hit the [Morse] key for a minute, boom, they’d get hit. We’d get gripes; here were [North Vietnamese] commanders on their telephones, saying, ‘I need a radio operator. My people won’t man the radios.’ Every time they’d open up with a radio, boom! There comes shot and shell . . . Oh hell, you know, you got to the point where you kind of sympathized with these poor bastards out there under that kind of shot and shell.”51

  The Invasion of Cambodia

  By early 1970 the Nixon administration was secretly planning to expand the war into neighboring Cambodia. In February, President Richard Nixon authorized a massive secret bombing campaign against North Vietnamese base camps and supply depots there. On March 18, Cambodian leader Prince Norodom Si-hanouk was overthrown in a coup d’état led by the Cambodian defense minister, General Lon Nol.52

  On April 30, Nixon ordered U.S. troops to cross into Cambodia and wipe out the vast network of North Vietnamese military headquarter complexes and base camps inside the country. Demonstrations immediately erupted across America, which led to the tragic encounter between Ohio Army National Guard troops and student protesters at Kent State University, which left four students dead.

  So secret were the administration’s plans that neither NSA nor the military SIGINT units in Vietnam were sufficiently forewarned. Lieutenant Colonel James Freeze, the commander of the ASA’s 303rd Radio Research Battalion at Long Binh, did not find out about the invasion until April 28, two days before it was due to begin. There was not a lot that NSA and the military SIGINT units in Vietnam could do in forty-eight hours to prepare for the invasion.53

  One of the main objectives of the invasion was to capture or destroy the headquarters of all North Vietnamese and Viet Cong forces fighting in South Vietnam, which was known as the Central Office, South Vietnam (COSVN). SIGINT collected prior to the invasion showed that the COSVN headquarters complex was located somewhere just inside Cambodia opposite Tay Ninh Province in South Vietnam. Throughout the incursion, U.S. Army and Air Force ARDF aircraft were able to track the movements of COSVN by listening to its radio transmissions as it retreated deeper into Cambodia, always well ahead of the slow-moving U.S. and South Vietnamese forces, which, SIGINT showed, never came close to capturing the headquarters.54

  The invasion of Cambodia prompted the North Vietnamese to expand their control over eastern Cambodia. By the end of May 1970, all U.S. and South Vietnamese forces had retreated back across the border into South Vietnam, and the North Vietnamese military was left with complete control over all of northeastern Cambodia. As an NSA historian put it, “few operations in American military history had such dismal consequences.”55

  This Is the End

  On January 27, 1973, Secretary of State William Rogers and his North Vietnam -ese counterpart, Le Duc Tho, signed the Paris Peace Agreement, and the last remaining U.S. forces were withdrawn from South Vietnam two months later, including the last remaining U.S. military SIGINT collection units. After the U.S. troop withdrawal was completed, in late 1973, the only remaining NSA presence in the country was the agency’s liaison staff in Saigon, as well as several hundred U.S. Army advisers who were engaged in trying to train and equip the South Vietnamese SIGINT service.56

  Things remained relatively peaceful until the fall of 1974, when SIGINT reporting coming out of NSA began indicating that the North Vietnamese were openly building up the strength of their military forces inside South Vietnam. SIGINT clearly showed that huge numbers of North Vietnamese troops and supplies, including tanks and armored vehicles, were flowing down the Ho Chi Minh Trail, and they were no longer being hindered by American air strikes. By January 1975, SIGINT showed that the North Vietnamese military buildup in South Vietnam had been completed. Everyone in Washington knew that the “final offensive” was coming soon.57

  The collapse of South Vietnam began with the North Vietnamese conducting a probing attack in January 1975 in Phuoc Long Province, in southern South Vietnam. After a short fight, the province swiftly fell, a preview of what was to come. Despite all SIGINT indications of a continued North Vietnamese military buildup throughout the south, on February 5 the CIA’s intelligence analysts made this prediction: “While we expect localized heavy fighting to re-sume soon, there are no indications of Communist plans for an all-out offensive in the near future.” On February 18, the CIA predicted, “heavy North Vietnamese attacks” by the end of the month, with the expected focus of the new offensive to be Tay Ninh City, north of Saigon.58

  The CIA analysts could not have been more wrong. In March, the all-out North Vietnamese offe
nsive commenced, not around Tay Ninh but across northern South Vietnam and the Central Highlands. NSA and South Vietnam -ese SIGINT somehow failed to detect the presence of at least three North Vietnamese divisions in the Central Highlands until the attacks began. City after city fell in rapid succession, and by the end of March the entire Central Highlands had been abandoned to the North Vietnamese. The NSA representative at the South Vietnamese SIGINT intercept center in Pleiku barely managed to get out of the city before it fell. As North Vietnamese forces streamed south virtually unopposed, the old imperial capital of Hué fell on March 22. In mid-March, SIGINT had detected a number of North Vietnamese strategic reserve divisions being hastily moved into South Vietnam for the final push.59

  As the North Vietnamese forces pushed southward toward the city of Da Nang, on March 26 NSA ordered the sole agency officer assigned to the South Vietnamese listening post in the city to get out immediately. The NSA officer drove to the Da Nang airport and managed to talk his way on board one of the last Boeing 727 aircraft to get out of the city. An NSA history notes, “He rode the overloaded airplane to Saigon with a Vietnamese child on his lap.” Da Nang fell to the North Vietnamese four days later.60

  As the North Vietnamese brought up reinforcements and supplies for the final push to take Saigon, a few hundred miles to the west the forces of the Cambodian government were rapidly collapsing. Since the U.S. invasion of Cam bo-dia in April 1970, the North Vietnamese–backed Khmer Rouge forces had me thodically captured most of the country from President Lon Nol’s poorly led government forces. By January 1975, Lon Nol’s troops held only a tiny island of territory surrounding the capital of Phnom Penh, and SIGINT reporting coming out of NSA and from U.S. military units based in neighboring Thailand showed that the Khmer Rouge were inching closer to the besieged capital. On April 11, a U.S. Air Force SIGINT unit in Thailand intercepted a message from the Khmer Rouge high command ordering the final assault on Phnom Penh. Ambassador John Gunther Dean was immediately ordered to evacuate all employees of the U.S. embassy and any other Americans remaining in Cambodia. U.S. military helicop ters had completed the evacuation by the end of the day on April 12. The city fell to the Khmer Rouge the next day.61

  In Saigon, Ambassador Graham Martin refused to believe the SIGINT reporting that detailed the massive North Vietnamese military buildup taking place all around the city. He steadfastly disregarded the portents, even after the South Vietnamese president, Nguyen Van Thieu, and most of his ministers resigned and fled the country. An NSA history notes that Martin “believed that the SIGINT was NVA deception” and repeatedly refused to allow NSA’s station chief, Tom Glenn, to evacuate his forty-three-man staff and their twenty-two dependents from Saigon. Glenn also wanted to evacuate as many of the South Vietnamese SIGINT staff as possible, as they had worked side by side with NSA for so many years, but this request was also refused. NSA director Lieutenant General Lew Allen Jr., who had taken over the position in August 1973, pleaded with CIA director William Colby for permission to evacuate the NSA station from Saigon, but even this plea was to no avail because Martin did not want to show any sign that the U.S. government thought Saigon would fall. So Glenn disobeyed Martin’s direct order and surreptitiously put most of his staff and all of their dependents onto jammed commercial airlines leaving Saigon. There was nothing he could do for the hundreds of South Vietnamese officers and staff members who remained at their posts in Saigon listening to the North Vietnamese close in on the capital.62

  By April 24, 1975, even the CIA admitted the end was near. Colby delivered the bad news to President Gerald Ford, telling him that “the fate of the Republic of Vietnam is sealed, and Saigon faces imminent military collapse.”63

  Even when enemy troops and tanks overran the major South Vietnamese military base at Bien Hoa, outside Saigon, on April 26, Martin still refused to accept that Saigon was doomed. On April 28, Glenn met with the ambassador carry ing a message from Allen ordering Glenn to pack up his equipment and evacuate his remaining staff immediately. Martin refused to allow this. The following morning, the military airfield at Tan Son Nhut fell, cutting off the last air link to the outside.

  A massive evacuation operation to remove the last Americans and their South Vietnamese allies from Saigon began on April 29. Navy helicop ters from the aircraft carrier USS Hancock, cruising offshore, began shuttling back and forth, carrying seven thousand Americans and South Vietnamese to safety. U.S. Air Force U-2 and RC-135 reconnaissance aircraft were orbiting off the coast monitoring North Vietnamese radio traffic to detect any threat to the evacuation. In the confusion, Glenn discovered that no one had made any arrangements to evacuate his remaining staff, so the U.S. military attaché arranged for cars to pick up Glenn and his people at their compound outside Saigon and transport them to the embassy. That night, Glenn and his colleagues boarded a U.S. Navy helicop ter for the short ride to one of the navy ships off the coast.64

  But the thousands of South Vietnamese SIGINT officers and intercept operators, including their chief, General Pham Van Nhon, never got out. The North Vietnamese captured the entire twenty-seven-hundred-man organization intact as well as all their equipment. An NSA history notes, “Many of the South Vietnamese SIGINTers undoubtedly perished; others wound up in reeducation camps. In later years a few began trickling into the United States under the orderly departure program. Their story is yet untold.” By any measure, it was an inglorious end to NSA’s fifteen-year involvement in the Vietnam War, one that still haunts agency veterans to this day.65

  CHAPTER 8

  Riding the Whirlwind

  NSA During the Johnson Administration:

  1963–1969

  Sic gorgiamus allos subjectatos nunc (We gladly feast on those who would subdue us).

  —MORTICIA ADDAMS, THE ADDAMS FAMILY

  The State of the SIGINT Nation

  Between 1961 and 1969, NSA grew from 59,000 military and civilian personnel, with a bud get of $654 million, to a staggering 93,067 men and women, 19,300 of whom worked at NSA headquarters at Fort Meade, in Maryland. The agency’s budget stood at over $1 billion.1

  As it quickly became larger than all the other U.S. intelligence agencies combined, it was developing and deploying cutting-edge technology that radically transformed how it collected and produced intelligence. Beginning in 1960, NSA’s highly classified Boresight project employed special equipment at Naval Security Group high-frequency direction-finding (HFDF) listening posts that could locate the source of the burst transmissions of Soviet submarines in the Atlantic and the Pacific.2Later in the 1960s, a new worldwide ocean surveillance SIGINT system was brought online called Classic Bullseye. An automated, larger, faster, and more capable HFDF system than previous manual versions, Classic Bullseye merged and modernized the naval SIGINT intercept and HFDF resources of all five UKUSA member nations. It enabled the United States and its SIGINT partners to track in near real time the movements and activities of Soviet warships and submarines around the world. By the early 1970s, the Naval Security Group Command was operating twenty-one Classic Bullseye stations around the world, which were integrated with eight stations operated by NSA’s UKUSA partners.3

  NSA also fitted out seven spy ships under the rather transparent cover description of “Technical Research Ships.” In June 1956, NSA director General Ralph Canine had recommended putting NSA intercept gear on U.S. Navy ships as a rapid-reaction force to cover contingencies in parts of the world where NSA did not have listening posts. Under pressure from the CIA in the late 1950s, NSA increased its SIGINT coverage of areas it had long neglected, particularly Latin America and Africa, where events commanded greater U.S. intelligence attention following the granting of indepen dence to former colonies by Eu ro pean nations. Small but bloody guerrilla wars, many communist-backed, broke out throughout Latin America, Africa, and Asia. To monitor all these developments, NSA built its own fleet of spy ships— patterned after the Russian spy trawlers that had lurked off American territorial waters since the early 1
950s— which were to be manned by U.S. Navy officers and crews but used exclusively for NSA.4

  With the launch of the first “ferret” electronic intelligence satellites by the National Reconnaissance Office (NRO) in the early 1960s, NSA also played an increasingly important role in space, its ELINT collection exponentially expanding what the U.S. intelligence community knew about the Soviet Union. Between 1963 and 1967, American ferret satellites mapped the locations and ascertained the capabilities of virtually every Soviet radar site in Eastern Europe and the Soviet Union, as well as all Chinese, North Korean, and North Vietnamese radar systems. By 1967, the ELINT database had enabled the CIA to issue its first truly comprehensive National Intelligence Estimate on the state of Soviet air defenses, an assessment based almost entirely on SIGINT.5

  Beginning in 1966, the U.S. intelligence community became alarmed about the nascent Soviet antiballistic missile (ABM) system that was then being constructed around Moscow. Given a November 17, 1966, U.S. Intelligence Board mandate, CIA director Richard Helms ordered his agency to develop—in a year or less—a new ELINT satellite to collect intelligence about Soviet ABM work. It was developed, produced, and launched by the NRO, and the first of the new ABM-intercept satellites went into orbit in early 1968. Colonel John Copley, head of the NSA division processing the satellite intercepts, later recounted, “By 1968 data from these payloads and the follow-on systems had identified early ABM-associated radars, greatly reducing the uncertainty associated with the Soviet strategic threat.”6

  To exploit the cornucopia of intercepted SIGINT data, NSA’s basement computer complex expanded dramatically in the 1960s, particularly with the advent of IBM’s development in the late 1950s of a revolutionary new data processor called Stretch, which was one hundred times more powerful than any other existing computer system. NSA’s deputy director, Louis Tordella, immediately ordered the computer. The first one, christened Harvest by NSA, was delivered in early 1962. With the capacity to read three million characters per minute, Harvest could do in minutes what older computers had taken weeks to accomplish. For example, in 1968 Harvest took only three hours and fifty minutes to scan seven million intercepts to see if they contained any of seven thousand words and phrases on a watch list, which equated to over thirty thousand intercepts scanned per minute. This huge computer system, the agency’s workhorse for the next fifteen years, is generally credited with helping NSA stay competitive in the code-breaking game throughout the 1960s and was reportedly instrumental in helping NSA solve a number of important Soviet cipher systems during the 1970s.7