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(8//8I) In mid-December, lronhorse sent its
first data to the TACC-NS on an unofficial basis.
Modifications continued to be made to the system
as it was being put through its routines. An
enhanced voice intercept position was installed to
accommodate the growing use of voice communications
by the North Vietnamese air surveillance
system. Software modifications to the interface
cleaned up the garbled tracks sent to the TACC.
By the middle of May 1968, lronhorse was considered
ready for operations. Even in its test
phase, the goal of faster data transfer had been
met and exceeded. Compared to Hammock,
Ironhorse reduced the time it took to send the
information to the TACC. The time dropped from
a range of a low of thirty seconds and a high
of two minutes to a low of eight seconds and a
high of one minute. Tracking data sent through
the navy's data distribution system were now
available anywhere from eight seconds to three
minutes instead of the previous twelve to thirty
minutes!"
CU) It is difficult to assess the effect of
lronhorse on the air war. This is because about
the time the system became operational, the
United States was dramatically reducing the
scope of the bombing campaign. On 31 March
1968, President Johnson announced the cessation
of bombing north of
the nineteenth parallel.
On 1 April 1968, the air
war over North Vietnam
came to a practical end.
Although some bombing
missions continued in the
southern portion of the
DRV, there was little reaction
to them by Hanoi's
fighters, since this was on
the edge of their effective
GCI range. The American
bombing effort swung its
emphasis to Laos. By 1
November, LBJ ordered a complete halt to bombing
over North Vietnam.
(8//8I) In April 1969, the Ironhorse complex
at Danang was seriously damaged by an explosion
of an adjacent Marine Corps ammunition
dump. Most of the equipment and software was
destroyed in the ensuing blasts and fire. Intercept
coverage was transferred to Air Force positions at
field sites in the Philippines and Thailand. The
Hammock system was resuscitated to handle the
input from these sites. Ironhorse operations at
Danang were not restored until July of 1969, but
problems with its communications and software
continued to plague the system until April 1970. 72
(8/SI) With the nexus of the air war now
located in the complex of U.S. air bases in
Thailand, Ironhorse eventually was shifted to the
7th RRFS at Ramasun, Thailand, and was
renamed Ironhorse II. In April 1971, the Danang
mission closed down, and its vans were shipped
to Fort Meade. The personnel from the 6924th
Security Squadron deployed to Thailand. From
then on, Ironhorse became just another input
into Combat Lightning, the USAF's C31 system
for the air war. Ironhorse continued to function
as part of the tactical air control system until the
~ Darnaqe to the lronhorse operations area caused by the 27 Aptil1969
arnrnunttlon dump explosion qt Dananq
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