spartans_in_darkness

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fact that the most important indicator, "N-Day,"
was discussed openly could be seen as a major
failure. Effective security programs, and related
denial and deception plans, have to identify such
potential indicators and work towards hiding
them or confusing the enemy as to their exact
nature. However, this was not the case for
Vietnamese plans for Tet. From as early as the
second week of January, cryptologists knew
about the significance of "N-Day." But, as we have
seen, the exact date remained unknown, and the
other indicators were never fully realized in the
NSA reporting. Then, again, the "N-Day" references
were confined almost exclusively to PAVN
units in the the B-3 Front, and could have been
part of a deception effort.
(8//81) In another sense, SIGINT may have
been a victim of its own success against PAVN
communications. In the months before Tet, and
especially in January, the overwhelming bulk of
the radio communications intercepted came from
PAVN units operating in the DMZ and the
Central Highlands. Viet Cong units moving into
positions in and around South Vietnam's urban
centers and military installations generated hardly
any communications. The ensuing reporting,
especially that in the NSA series on the general
offensive, reflected this emphasis on the PAVN's
activities, while the VC efforts were almost entirely
missed. This picture of communist preparations
coincided with Westmoreland's view; in
fact, it may have stimulated his thinking about
the communist plans.'"
CD) In fact, this is a variation of the classic
"Ultra syndrome," in which commanders come to
rely almost exclusively on signals intelligence.
Since the only SIGINT came from the intercept of
PAVN communications, then its activity became
the focus of MACV'sattention. Last minute intelligence
from South Vietnamese sources - the capture
of enemy soldiers who gave away the attack
plan - was too little and too late to influence
thinking away from the seeming PAVN threat to
Khe Sanh and the Central Highlands.'"
(8//81) Another reason has been put forward
to explain the inability of American SIGINT
to report completely the scope, intensity, and specific
targets of the Tet attacks: the arrangement
of American intercept sites in South Vietnam precluded
coverage of communist communications
in the southern part of the country. This explanation
maintains that, since the major U.S. SIGINT
sites were clustered in the northern part of the
country, and their missions were concentrated on
those regions, the preponderance of their intercept
was therefore on the communist preparations
in the Central Highlands and the northern
provinces. This bias led to the conclusion that the
main thrust of the communist forces would be in
those two regions.Y'"
(8//81) Actually, this argument's presumption
of an exclusive configuration of U.S. SIGINT
sites in the northern and eastern arts of South
Vietnam is not correct. First of all,
"--- ..... five ASA intercept sites
located in the III CTZ, which includes the region
around and to the north of Saigon.'" The ASA
sites were tactical SIGINT units attached to U.S.
combat formations based throughout the area. All
of these sites]
~ere
intercepting communications from Viet /Cong
combat units and military intelligence elements
in and around the Saigon region. Another unit,
the ASA146th Aviation Company, also performed
intercept and ARDF missions in support: of these
sites. Additionally, another station, the ASA site
at Bien Hoa, took the intercept from the other
seven sites and was issuing reports and translations
on the activities by Main Force Viet Cong
units such as the 9th and 5th Light Infantry
Divisions and their subordinate units in Bien Hoa
and Phuc Long provinces. This reporting by the
ASA site at Bien Hoa continuedin its own series
and was repeated in the Southeast Asia SIGINT
EO
EO
1.4. (c)
1.4. (d)
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