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Earlier, NSA had succeeded in intercepting a weak beacon transponder
signal transmitted from a small spiral antenna on the tail of the Soviet


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SA-2 surface-to-air missile. This antenna transmitted the SA-2's
navigational data back to the launch site. "It came on thirty seconds after
the missile's launch," said one former NSA official, "so that the launch
site can track the missile and steer it close enough to where its own
homing system will lock on to the target and go in for the final kill."
Once such a signal had been captured and dissected by NSA,
however, technicians were able to secretly jam the signal, sending the
missiles off course and saving the lives of hundreds of pilots. But in 1972
the North Vietnamese realized something was very wrong and called in
the Soviets to help correct the problem. Shortly thereafter the frequencies
were changed and the SA-2 missiles once again began hitting their mark.
Despite months of effort, intercept operators were not able to
recapture the faint signal. Then, in late 1972, someone at NSA
headquarters recalled a pet project by a Navy cryptologic officer. Using
spare, off-the-shelf equipment, he had put together a unique signal
acquisition system. Within twenty-four hours, the officer, John Arnold,
was sent off to Southeast Asia with his experimental machine and
assigned to the USS Long Beach. Arnold's machine worked better than
anyone could have anticipated. Once again, they were able to intercept
the elusive SA-2 signal, and the hit-kill ratio switched back to America's
favor. "They dumped more than a million dollars in other systems and
platforms trying to find the answer and they couldn't," said Arnold.
By 1972, NSA also began "remoting" some of its more hazardous
operations. Rather than having intercept operators sit in front of row
after row of receivers, spinning dials to find enemy voices, now the
agency could do much of its eavesdropping by computer.
Codenamed Explorer, the system involved preprogrammed computers
and receivers that would quickly scan for targeted and unusual
frequencies carrying voice and coded communications. Once located,
they would be uplinked to an aircraft or satellite and then, through a
series of relays, downlinked to NSA or some other safe location away
from the fighting. There, translators, codebreakers, computers, and
traffic analysts could dissect the signals. A similar system, codenamed
Guardrail, was established in Europe. In Guardrail, an aircraft was used
as a relay to move Sigint from the front lines to analysts in the rear.
Explorer was particularly useful in unusually dangerous areas” for
example, just south of the DMZ. To capture those communications, the
system was set up on several remote firebases located on high and
isolated hills. One was Firebase Sarge and another was known as A-4.
Although Explorer was highly automated, several people were
nevertheless needed to maintain the equipment and keep it from being
vandalized, a very hazardous job given the locations.
The firebases just south of the DMZ were the most isolated and


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dangerous listening posts in the world. There, intercept operators were
close enough to the dragon to count its teeth. Occasionally they would
also feel its sting. A-4 sat on the top of a steep mountain near Con Thien.
"From A-4 you could see the middle of the DMZ, it was that close," said
an intercept operator stationed there. "It was the furthest northernmost
outpost the Americans held in Vietnam. The DMZ looked like rolling hills;
a no-man's-land with a river through it and scrub brush and that was
about it for miles. There was no fence. The river separated it and over the
river was a bridge and the NVA flew a big flag over it with a red star and
you could see it through binoculars. We used to watch them infiltrate,
you could watch them come across. At the time there were no other
Americans there."
Working in a tiny underground bunker, the handful of intercept
operators pinpointed enemy infiltrators, artillery units moving toward the
border, and mobile surface-to-air missiles through voice and coded
intercepts. "In A-4 we were in a bunker underground," said the intercept
operator. "They had the codes broken, they could pick up the firing
designators. When the North Vietnamese got on the radio to open up the
guns or the rocket attack, they would use designators. And the
Americans knew the designators, so we would know when we were about
to get shelled and we would go back underground so we didn't get blown
up."
The concrete bunker was about ten feet underground and held only
about five to seven intercept operators. Five worked the intercept
equipment while the other two slept. They would take turns and they
were all volunteers. Nearby was another bunker containing the NSA
Explorer remote intercept equipment.
In early 1972, the intercept operators at A-4 began getting indications
of something larger than the usual infiltration or harassment taking
place across the border. "We thought there was going to be an invasion,
and nobody was really listening," said one intercept operator who was
there at the time. "That was January, February, beginning of March
1972. There was just too much buildup of activity above the DMZ for it
not to happen. We were reporting that to the higher-ups. But in my
personal opinion, it fell on deaf ears because at that time there weren't
any Americans except for the intelligence people and then the few
American advisers who were up there."
Further to the west, at Firebase Sarge, indications of a major attack
were also becoming more numerous. There, the only Sigint personnel
were two Army specialists, Bruce Crosby, Jr., and Gary Westcott,
assigned to maintain the Explorer equipment contained in a bunker. The
only other American was Marine Major Walter Boomer, who was an
adviser to South Vietnamese forces assigned to the firebase. Earlier in
March, Boomer had warned General Giai, the commanding general of the


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South Vietnamese Army's 3rd Division, of his deep concern about the
steady increase in enemy activity in the area. He told Giai that he felt
that something significant was going to take place soon. The general
listened but said there was little he could do.
To the south, at Cam Lo, a secret American facility monitored the
DMZ through ground-surveillance devices planted throughout the zone.
During most of March, the number of trucks detected crossing the DMZ
had tripled, and the monitors recorded both wheeled and tracked vehicle
traffic, a worrisome sign. By the end of the month, the monitors were
recording heavy traffic even during daylight hours, something that had
never happened before.
The bad news came on Good Friday, March 30, 1972. Just before
noon on Firebase Sarge, Major Boomer passed on to his headquarters
some disturbing news. "Shortly after daylight the NVA began to shell us
here at Sarge," he said. "The NVA's fire is as accurate and as heavy as we
have ever experienced up here. We're all okay now, but there is probably
a big battle coming our way. ... It looks like this could be their big push."
It was Tet all over again. The North Vietnamese Army had launched
their largest offensive in four years, and U.S. and South Vietnamese
forces were just as unprepared as they had been the last time. In fact,
the U.S. military command in Saigon, 350 miles south, refused to believe
a major attack was in progress even after it had begun. Over 30,000 well-
armed soldiers supported by more than 400 armored fighting vehicles,
tanks, mobile missile launchers, and long-range cannons poured over
the DMZ. Crossing the Ben Hai River, they knifed into the South's Quang
Tri Province and turned the lonely firebases, like islands in the sky, into
shooting galleries.
Up on Firebase Sarge, as the earth rolled from the violent assault,
Boomer ordered Westcott and Crosby to remain in the NSA Explorer
bunker and keep in radio contact with him and also with the listening
post at A-4. Explorer was housed in an aluminum hut that also
contained eight pieces of NSA crypto equipment. Around the hut was a
bunker made of several rows of sandbags and a steel roof covered with
another five feet of additional sandbags. For ventilation there was a
window on one side.
Below Sarge, Soviet 130mm guns, the size of telephone poles, let loose
with boulderlike shells. The rattle of small-arms fire followed and then
the heavy crump of 122mm rockets raining down. Suddenly both A-4 and
Boomer lost contact with Westcott and Crosby. Shortly after noon, a
rocket scored a direct hit, crashing through the window in the NSA
Explorer bunker. The two intercept operators were killed instantly and
the bunker became a crematorium, burning for days. More than a decade
after the first Sigint soldier died in Vietnam, two of the last were killed.



290
With A-4 also under heavy assault, the intercept operators were
ordered to begin destroying Explorer and the rest of the crypto
equipment and files. Above each of the sensitive devices were thermite
plates for quick destruction. The plates were electrically activated and
were wired together to a switch on the outside of the hut. Each thermite
plate” about a foot wide and an inch thick”was designed to burn at the
solar-like temperature of 35,000 degrees Fahrenheit. "The hut would
burn for a couple of days before all the metal essentially turned to ash,"
said one of the soldiers who installed the destruction devices. "Once the
thermites reached full temperature and the hut started burning no one
could possibly survive and in the end there would be nothing left,
absolutely nothing." Within a day of what became known as the Easter
Offensive, there was no evidence that NSA had ever been at A-4, just
ashes. The war was over and the United States had lost.
On January 27, 1973, the United States and Vietnam signed a cease-
fire agreement. At 7:45 A.M., fifteen minutes before the cease-fire took
effect, the USS Turner Joy, which had helped launch America's
misguided adventure, sailed off the Cam Lo”Cua Viet River outlet and
senselessly fired off the last salvo of the war.


Six months later, after barely a year in office, Samuel Phillips left NSA
to head up the Air Force Space and Missile Organization. The man
chosen to finish out his assignment was Lieutenant General Lew Allen,
Jr. Tall and professorial-looking, with rimless glasses and a few wisps of
fine dark hair across his crown, Allen, an expert in space
reconnaissance, arrived at NSA following an assignment of only five and
a half months with the CIA.
The new director arrived in time to watch events in Vietnam rapidly
deteriorate. By 1975 American troops were out of the country and the
Communist forces in the north were pushing south in an effort to finally
consolidate the nation and their power. Their secret goal was to capture
Saigon by May 19, the birthday of Ho Chi Minh, who had died in 1969, at
the age of seventy-nine.
By April the endgame was near. At four o'clock on the morning of
April 29, Saigon woke to the sound of distant thunder: heavy artillery fire
on the outskirts of the city. Residents broke out in panic. Any hope that
the U.S. Embassy staff and remaining Americans would be able to
conduct a somewhat dignified departure by aircraft was dashed when
explosions tore apart the runways at Tan Son Nhut Air Base. The only
thing left was Operation Frequent Wind, the emergency evacuation by
helicopter.
Two hours after the NVA arrived in the outskirts of Saigon, at 6:10
A.M., NSA's national cryptologic representative there signed off for the


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last time. "Have just received word to evacuate," he wrote in his
Secret/Comint Channels Only message, "exclusive" for Lew Allen. "Am
now destroying remaining classified material. Will cease transmissions
immediately after this message. We're tired but otherwise all right. Looks
like the battle for Saigon is on for real. ... I commend to you my people
who deserve the best NSA can give them for what they have been
through, but essentially for what they have achieved." Four days earlier,
NSA's operations chief in Saigon, Ralph Adams, had been ordered out. "I
took the last fixed-wing aircraft out of Saigon," he recalled. "Don't ever
want to do that again. I watched an entire nation just crumble. It was
scary as hell."
In the sullen heat, the repeated sounds of "White Christmas" over the
military radio station was surreal, as it was supposed to be. It was the
signal for the last Americans to quickly get to their designated removal
points. The U.S. embassy suddenly became a scene out of Dante. Mobs
of Vietnamese, including many who had cooperated with the United
States and had been promised evacuation, stormed the walls and pushed
against the gate. A conga line of helicopters took turns landing on the
embassy's roof, their blades barely slowing. Americans and Vietnamese
relatives and helpers ducked low and climbed on board to be whisked
away to an American naval flotilla in the South China Sea. Other
choppers, flown by escaping South Vietnamese pilots, made one-way
flights to the flattops and were then pushed into the sea, like dead
insects, to make room for more rescue aircraft.
Largely deaf as to what was going on fifty miles away in Saigon, the
commander of the flotilla asked NSA to lend him an ear. A short time
later an intercept operator tuned in on the embassy's communications
and continuously recounted events, minute by minute, to the flotilla.
With the beginning of Operation Comout, NSA, the ultimate voyeur,
secretly began eavesdropping on the final agonizing gasps of the Vietnam
War.
At 7:11 P.M. the NSA intercept operator reported:


THEY CANNOT GET THE AMBASSADOR OUT DUE TO A
FIRE ON TOP OF THE EMBASSY. CINCPAC [Commander-in-
Chief, Pacific] REPORTED THEY CANNOT CONTINUE THE
EVACUATION PAST 2300 [11:00 P.M.] LOCAL AND IT IS
IMPERATIVE TO GET ALL OF THE AMERICANS OUT.


Ambassador Graham Martin sat in his third-floor office, his face
ashen as his diplomatic post crumbled around him. Henry Boudreau, an
embassy counselor, walked in and was taken aback. "I saw the
ambassador briefly and was startled at how hoarse he was, how barely


292
able to speak. The pneumonia had all but wiped him out."
Earlier that morning his black, bulletproof Chevrolet limousine had
carried him to the U.S. compound, still in a state of disbelief. For weeks,
as the North Vietnamese Army closed in on Saigon, Martin had refused
to accept the inevitable. He believed that a face-saving exit was still
possible. "Goddamnit, Graham!" shouted a frustrated Washington official
in Saigon to help with the evacuation. "Don't you realize what's
happening?" Drifting in from the hallways was the bitter scent of smoke
from incinerators crammed too full of thick files and endless reports. By
now, desperate Vietnamese were camped in every part of the embassy,
their life's belongings held in torn paper bags. Children with puffy cheeks
and frightened eyes clung tightly to their mothers' long ao dais.


NSA: 7:13 PM
NO AMBASSADOR [present]. THERE ARE STILL MANY
U.S. PERSONNEL AT THE EMBASSY.


Martin had insisted that Americans not be given preferential
treatment over Vietnamese in the evacuation, but this rule, like most,
was ignored as U.S. officials pushed to the head of the line.


NSA:11:28PM
THE AMBASSADOR WILL NOT, RPT NOT LEAVE UNTIL
THERE ARE NO MORE PERSONNEL TO BE EVACUATED.
HE STATES THAT ALL PERSONNEL WITHIN THE
COMPOUND ARE EVACUEES.

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