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With the passing of the Tonkin Gulf Resolution, the tidal wave that
had begun as distant whitecaps came crashing down, eventually
sweeping tens of thousands of Americans to their death.
At the same time the war was being fought in the steamy jungles, it
was also being waged high in the ether. This was the Sigint war, an
invisible battle to capture hidden electrons and solve complex puzzles. As
in World War II, it can often be the decisive battle. But the glory days of
solving the German Enigma code and the Japanese Purple code had long
since passed. With the North Vietnamese military and the Vietcong, NSA
was discovering, the old rules had been changed. The eavesdroppers
would have to start from scratch.
Hidden from view, NSA rapidly increased its buildup in Vietnam. By
1964 the number of cryptologic personnel in the country had reached
1,747. Three hundred men now packed Davis Station at Tan Son Nhut in
Saigon. The Navy sent a Marine Sigint detachment to Pleiku, where they
targeted Laotian and North Vietnamese communications. And U.S. Air
Force intercept operators began setting up shop in Da Nang. To
coordinate the growing numbers of units, a secure communications
network was built linking sites at Nha Trang, Can Tho, Bien Hoa, Pleiku,
Da Nang, and Ban Me Thuot. Then, in order to communicate quickly and
securely with NSA headquarters, an undersea cable was laid from
Vietnam to the Philippines. Codenamed Wetwash, the cable carried a
variety of traffic ranging from high-speed CRITIC circuits to intercepted
North Vietnamese messages too difficult to decrypt in Vietnam. In the


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Philippines, the Wetwash cable connected to another secure undersea
cable that eventually terminated at NSA, in Fort Meade.
In the far north, near the demilitarized zone separating North from
South, 1,000 Sigint personnel were sent to Phu Bai, which became the
cornerstone of NSA's expansion. Like electronic border police, intercept
operators manned 100 positions in a windowless operations building,
listening for indications of infiltration and guerrilla activity. Others
eavesdropped on tactical communications by both North Vietnamese and
Laotian Communist forces. The expansive base was supported by
another 500 people and surrounded by high fences, barbed wire and
concertina wire, and eleven guard posts manned twenty-four hours a
day.
But just as the numbers of people continued to grow, so did the
problems. Although the school to train South Vietnamese soldiers was
built and fully equipped, for years it had virtually no students because of
the inability of the indigenous soldiers to pass NSA's rigorous security
clearance requirements. More equipment and personnel in the field
meant more intercepts, but most of them were not being analyzed
because of the lack of trained linguists. "U.S. personnel with the ability
to read Vietnamese texts were in short supply," said one NSA document,
"and people competent to deal with spoken Vietnamese, with very few
exceptions, were not to be found." Despite a crash training program at
NSA, said the report, "the linguist problem became worse, not better."
Communications problems were also frequent.
Most incredibly, NSA deliberately refrained from mounting a massive
World War II”style Enigma or Purple effort against North Vietnamese
cipher systems. According to one of the key NSA officials overseeing the
cryptologic effort in Vietnam, "We found that we had adequate
information without having to do that. In other words, through a
combination of traffic analysis, low-level cryptanalysis, and
plaintext/clear voice. The situation didn't justify the major effort."
According to another former official, mounting an enormous effort
against North Vietnam would have diverted limited resources away from
"the Soviet problem" and other areas, which nobody wanted to do. "And
of course there was always the question of whether there was any utility
in working on one-time pads," said the former official. "But my argument
always was, How do you know it's a one-time pad if you don't work it?"
This was an allusion to the surprising "Venona" breakthrough in Soviet
onetime pads.
For most of the intercept operators, used to the monotonous routine
of peacetime listening posts, there was an air of unreality about Vietnam.
The constant wharp-wharp-wharp of steel helicopter blades echoing off
rusty corrugated roofs. Gunships on a hunt, flying in formation as they
skimmed the ground. Open crates of green rocket-propelled grenades


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and saucer-shaped claymore mines resting haphazardly beside delicate
flame trees and baskets of lotus blossoms.


The Sigint war was fought by both sides. Although no one knew it at
the time, the North Vietnamese Central Research Directorate, which
managed the North's Sigint operations, was successfully collecting
almost all South Vietnamese and U.S. communications passing over a
number of key traffic lanes. North Vietnam did not need to break high-
level American codes, because the Americans continuously chose
expediency over security. Rather than take the time to send the
information over secure, encrypted lines, they would frequently bypass
encryption and simply use voice communications. The problem became,
according to NSA, America's Achilles' heel during the war. "There was no
blotter large enough to dry up sensitive, exploitable plain-language
communications in Vietnam," said one NSA report.
Over the years, U.S. forces would occasionally capture enemy Sigint
operators who would shed light on the problem. "Through interrogation
of these men and study of the documents and signals intelligence
materials seized," said a secret NSA analysis, "a clear, even frightening
picture of Vietnamese Communist successes against Allied
communications gradually emerged." Even as late as 1969, major
clandestine listening posts were being discovered, such as one in Binh
Duong Province. "Evaluation of the equipment showed that the enemy
unit could hear virtually all voice and manual Morse communications
used by U.S. and Allied tactical units. The documents proved the
enemy's success”2,000 hand-copied voice transmissions in English and
signals intelligence instruction books of a highly professional caliber."
U.S. intelligence sources estimated that North Vietnam had probably
as many as 5,000 intercept operators targeting American
communications. "The inescapable conclusion from the captured
documents in U.S. hands," said the NSA report, "is that the enemy is
conducting a highly sophisticated signal intelligence operation directed
against U.S. and Allied forces in South Vietnam. He has developed the
art of intercept to the point where his operators receive training materials
tailored to the particular U.S. or Allied units against whom they are
working. The training materials captured list selected [U.S.] units, the
frequencies on which they communicated, their communications
procedures, the formats and numerous examples of their messages, and
other characteristics to guide the communist operator."
The consequences of the poor U.S. communications security coupled
with the advanced state of North Vietnamese Sigint were serious. NSA
labeled the careless procedures "deadly transmissions." Lieutenant
General Charles R. Myer, a career signals officer who served twice in



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Vietnam, outlined the problem. "The enemy might disappear from a
location just before a planned U.S. attack," he said. "B-52 bomber strikes
did not produce expected results because the enemy apparently
anticipated them."
Strikes from sea were equally vulnerable. On February 11, 1965, the
aircraft carrier USS Hancock was preparing to launch a bombing raid
against certain shore targets in the North. But details of the mission were
discussed over plain-language channels days before the attack. As a
result, North Vietnamese naval units were ordered to use camouflage and
systematically disperse before the morning of February 11. On other
occasions, when the American planes arrived over their targets, anti-
aircraft weapons were waiting, pointing in their direction, with deadly
results.
Again in an attempt to avoid the time-consuming task of encrypting
information using approved NSA ciphers and equipment, Americans
would often make up their own "homemade" codes. "Their continued
appearance on the scene has constituted one of the major Comsec
[communications security] headaches of the war," a Top Secret/Umbra
NSA report noted. "Even as late as the spring of 1969, the U.S. Air Force
attach© in Laos, who was coordinating semi-covert U.S. air and other
operations in that country, was sending most of his messages in a code
he had made up himself." NSA's Air Force communications security
specialists secretly eavesdropped on the attach©'s communications.
"They could completely reconstruct his code within eight to ten hours
after each change," said the NSA report. "Since the attach© changed
codes only every five weeks, most of his messages were susceptible to
immediate enemy Sigint exploitation. The appearance and reappearance
of codes of this type demand constant Comsec alertness."
Even if U.S. forces did use secure encryption to pass sensitive
information, such as dates and times for attacks, problems arose when
that information was passed to the South Vietnamese military and they
discussed it over less secure channels. The South's communications
were particularly vulnerable to the Vietcong. For example, using
captured American equipment the guerrilla force was able to pick up
U.S. Special Forces communications transmitted through the South
Vietnamese Air Force network. "It was . . . likely that they could gain all
the intelligence they needed on the growing U.S. presence in Vietnam
from [South Vietnamese Air Force] communications," said an NSA study
of the problem. One former Vietcong soldier later told U.S. officials that
as a result of Sigint his unit had never been taken by surprise over a ten-
year period and that they never had enough English-language linguists
for all the communications they intercepted.
Another major problem was the lack of secure telephones. The
Vietnam-era secure phone, the KY-8, was far from the compact handset


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of today; it looked more like a small safe. In 1965 there were 800 of the
crypto machines in a warehouse in the U.S., but they had neither
mounting brackets nor connecting cables. After what was described as
"some tortuous evolutions," the first KY-8s eventually arrived in South
Vietnam late in 1965 and over the next three years they were all
distributed. An aircraft version, the KY-28, and a mobile unit, the KY-38,
were also distributed. But there were not nearly enough secure phones.
They were also very temperamental and prone to failure. Because they
broke down in direct sunlight and high heat, they were also useless in
places like bunkers. As a result, they did not solve the problem of
classified talk on unsecure phones. "Signal security, particularly in voice
radio transmissions," said General Myer, "was a major problem area
throughout the period of combat operations in Vietnam."
To help guard against sloppy procedures and compromises, NSA and
its naval, air, and military arms conducted what was known as
communications security monitoring. "In conventional Comsec
operations," said one NSA study of the Vietnam War, "the monitor places
himself in the role of the enemy. Selectively, he intercepts the
communications of his own service and then reports on the intelligence
he has”and the enemies could have”gleaned from them." The Comsec
personnel would frequently work from the back of hot, antenna-covered,
three-quarter-ton trucks. Surrounding them would be a variety of
monitoring equipment, such as the TPHZ-3, which could listen to thirty
telephone lines simultaneously. During 1967, Comsec operators
eavesdropped on 6,606,539 radio-telephone conversations and more
than 500,000 conventional telephone calls.
At one point, such operations possibly saved the life of Lieutenant
General Creighton W. Abrams, the deputy chief of the U.S. military
command in Vietnam. As Abrams was about to board a helicopter on a
flight north from Saigon to Phu Bai near Hue, the details of the mission,
including the time, altitude, and route, and the names of the passengers,
were transmitted in the clear. Comsec monitors overheard the
transmission and reported it immediately. As a result, the flight plan was
changed. North Vietnamese intercept operators also overheard the
transmission. Although Abrams flew by a different route, one of the other
helicopters scheduled to make the trip was not told of the change. As a
result, "it was shot at the whole way from Saigon to Phu Bai”an
unusual effort by the VC who did not usually shoot at helicopters on
such flights," said an NSA report on the incident. "This I believe was a
certain example of enemy Sigint use."
North Vietnamese Sigint experts were also able to pass false and
deceptive information over U.S. communications links and at other times
were able to trick American personnel into passing sensitive information
to them over the phone. NSA called such "imitative communications


257
deception (ICD)" the "capstone of the enemy's Sigint operations." During
one period, at least eight American helicopters were downed as a result
of ICD.
At the U.S. air base in Da Nang, a Vietcong guerrilla killed an
American base guard and then picked up his phone. Speaking English,
he announced that the far end of the base was being attacked. When the
guards rushed off to the far end of the field, the Vietcong attacked with
little resistance. The damage to the base and its planes was estimated to
be around $15 million. The incident could have been prevented if the
guards had simply used a proper authentication system.
At another point, guerrillas were able to lure American helicopters
into a trap by breaking into their frequencies, using correct call signs,
and then directing the choppers to a landing spot where they were
ambushed. There were also numerous times in which American air and
artillery strikes were deliberately misdirected to bomb or fire on friendly
positions. At other times, the guerrillas were able to halt attacks by
giving false cease-fire orders.
Even the best NSA encryption systems then available were potentially
vulnerable. These included the KY-8 for secure voice communications
and the KW-7 for highly sensitive written messages. "All of our primary
operational communications were passed on KW-7 secured circuits," one
U.S. commander in Vietnam told NSA. "Thus, for the more important
traffic, we had good security."
But both the KW-7 and the KY-8 were captured by North Korea and
turned over to Russia in 1968, and for years, until long after the Vietnam
War ended, the Soviets were also getting up-to-date keylists for the
machines from the Walker spy ring. This has led to speculation that the
Soviets passed some of this information to the North Vietnamese.
Former KGB Major General Boris A. Solomatin, chief of station at the
Soviet Embassy in Washington from 1965 to 1968, denies that Walker
contributed to America's defeat: "Walker is not responsible for your
failures in bombing in North Vietnam." Solomatin, who retired from the
KGB and still lives in Moscow, added, "If you decide that the information
from Walker was not handed over to the North Vietnamese or our other
allies, you will be making the correct one."
But Solomatin's deputy at the time, KGB Major General Oleg Kalugin,
who defected to the United States and now lives in Washington,
disagrees. Although the machines and their keylists were considered far
too sensitive to turn over to the North Vietnamese, the Russians certainly
helped the North Vietnamese whenever they could. "We certainly
provided the Vietnamese with some of the product we had obtained
through John Walker, and ultimately with the Pueblo's stuff we had from
the North Koreans," said Kalugin. "The Soviet military were . . . quite


258
involved in Vietnam. Not only in terms of providing military equipment,
hardware and weapons, but also in helping the Vietnamese to conduct
military operations, and to brief them on certain issues which the Soviets
thought would have winning implications for the Vietnamese side."
Kalugin added, "By providing the intelligence we had obtained . . . I'm
sure we would help the Vietnamese. I'm sure we did."
The Soviets also provided help in other ways. On June 18, 1965, on a

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