spartans_in_darkness

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1.4. (e)
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would be going up against an air defense system
which had barely come into being a few years earlier
Yet, by war's end, the North Vietnamese air
defense system evolved into a sophisticated structure
which required the United States to develop
extensive and steadily enhanced efforts in intelligence
and countermeasures to neutralize it. Even
then, each side would have to struggle to regain a
superiority that often would be fleeting.
(T8//81) The DRV's air defense network's
CIt was composed of about forty or so visual'
observation posts scattered throughout the country
whose job was to report aerial activity. Their
reports went to a so-called filter center in Hanoi,
which in turn would send the tracking information
to a sector headquarters which controlled
antiaircraft artillery (AAA) units." Hanoi's inventory
of antiaircraft artillery included typical communist
hardware such as 12.7mm, 37mm flak
and, interestingly, the famous German 88mm
antiaircraft guns with a Wurzburg targeting radar
obtained from China in late 1954. 9
(8//81) Messages carrying information on aircraft
were sent via high-freauencv manual morse
communications.I
Uhey took the form of what is knmvn as a proforma
message, that is, a single line of digits or
letters representing categories of information on
the flight: direction, altitude, speed, identity, and
type of aircraft. Tracking messages of individual
flights could take as long as thirty minutes to pass
through the system from initial observation to the
point where the filter center would issue orders
for continued tracking.
'--
...... Interestingly,
the basic framework of the DRV air defense network
and its communications would remain fundamentally
in place through all of the various
upgrades and additions during the years of the air
war. This would allow American cryptologists to
exploit Hanoi's communications for tactical
applications during the years of the air war.
ET8//8I) The expansion of the DRV's air
defense system continued
lAs
a result of an increase in the number of radar stations,
the North Vietnamese increased their filter
centers, adding one for the southern regions at
Vinh, and another to the northwest at Na San.
The number of AAA battalions had increased to
ten, although communications serving these
units had not been recovered by late 1962. No
fighter aircraft were in the North Vietnamese
inventory. Two airfields were determined to be
able to support jet aircraft. In this case, it was
assumed that jet fighters from the PRC would
actually use the strips."
(8//81) Functionally, the DRV's air defense
command and control communications were
composed of four main capabilities. First, there
was an air warning (AW) capability which
employed radar and, to a limited degree, the old
visual surveillance system which gave Hanoi early
warning information on air strikes. Secondly,
there was an air surveillance capability which
provided preflight and in-flight information on
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