Field ArTillery - US Army Center Of Military History

282 The OrganizaTiOnal hisTOry Of field arTillery
deployed at the corps level. 29 Battery C, 2d Battalion, 26th Artil lery, operating
along the demilitarized zone in the I Corps tactical zone, was the only unit using
sound-ranging equipment. That equip ment (GR–8 sound-ranging sets) was originally
issued in 1945. A limited supply of parts, a limited number of technically quali fied
maintenance personnel, the long wire lines and heavy equipment, survey requirements,
and a lack of con sideration of the need to modernize the old sets hindered
the employment of the sound-ranging platoons considerably. Flash ranging was also
used, primar ily along the demilitarized zone. 30 Searchlights could produce either
visible or infra red lighting, and they were oriented for direc tion on the same angular
refere nce as the artillery pieces.
Sensors were also effective means of target acquisition. Intelligence elements
were responsible for employing sensors, but they worked in close cooperation
with the artillery; the best means of fire support that could respond
quickly to sensor activities were the pre-positioned field artillery pieces. The
sensors used in Vietnam were emplaced by hand or delivered from aircraft in an
anti-infiltration role. They sensed the intrusion of enemy vehicles and troops
seismically, acoustically, electro magneti cally, or through infrared devices. Information
on the direction of movement, the size of the force, and the length of the
columns could all be gained through the use of sensor fields. Troops in Vietnam
also used sensors in support of the barrier system south of the demilitarized zone.
Many of the sensors designated for this role were diverted in the spring of 1968
to support the defense of Khe Sanh. As the sensors became available to ground
force commanders, the results were noteworthy, and these successes spurred their
further use and development. 31
To locate targets, direct-support artillery battalions used countermortar radars,
ground surveillance radars, and even the shorter-ranged infantry antipersonnel radars.
Artillerymen in Vietnam considered the ground surveillance radar (AN/TPS–25)
to be valuable equipment, although the heavy rainfall and dense foliage hindered
its effectiveness. Less favorable evaluations accompanied the countermortar radar
(AN/MPQ–4), which had had a small scanning sector and could not locate such
low-trajectory weapons as rockets. The use of several radars to provide mutual
and overlapping coverage eased the first problem, but the second was not easily
correctable because the radars had been designed specifically for detection of
high-trajectory weapons (such as mortars). For nondivisional units, radar detach-
30 Coffman, “Sound Ranging,” p. 23. See also FA School Annual Historical Summary, 1969, pp.
14–15, copy in CMH files.
31 Ott, Field Artillery, pp. 73–74; Louis C. Friedersdorff and John P. Bulger, “Field Artillery Applications
for Remote Sensors,” Field Artillery Journal, January-February 1977, pp. 54–56; Pearson,
Northern Provinces, pp. 21–24.
32 [Col] Hobby, “Artillery Target Acquisition in Kontum Province,” 1971, copy in FA School files;
Ott, Field Artillery, pp. 179–81; MTOE 6–517TP00 (countermortar radar detachment), 25 Jun 1968;
MTOE 6–302GP02 (ground surveillance radar detachment), 5 Feb 1970; FA School Annual Historical
Summary, 1969, pp. 15–16, copy in CMH files.