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approaches to the Da Nang Airbase and protected the vital bridges
across the Cau Do and Tuy Loan Rivers, south of the airbase.*

The two Marine infantry regiments, the 5th and 7th Marines, and the 3d Amphibian Tractor Battalion were responsible for the protection of the regions south of the Cau Do and north of the Cu De Rivers. On the division left, or most eastern sector, the amphibian tractor battalion patrolled the sand flats along the coast south of the Marble Mountain facility. South and west of the "amtrackers" and north of the Thanh Quit River, the 5th Marines with two battalions, the 2d Battalion, 3d Marines and the 3d Battalion, 5th Marines, maintained its area of operations. With the north-south railroad track serving as the boundary between the two regiments, the 7th Marines with all three of its battalions provided the shield in the western and northern reaches of the division area of operations. The 2d Battalion, 5th Marines, under the direct control of the division, operated in the An Hoa sector, located in the southwest corner of the division TAOR south of the Thu Bon River. To the east of the 7th Marines and south of the 5th Marines, the Korean Marine Brigade began its deployment into the Dai Loc corridor between the Thanh Quit and the Ky Lam.

With the introduction of enemy long-range 140mm and 122mm rockets
in February and June respectively of the previous year against the Da
Nang base, the Marine division took several countermeasures. It established
a rocket belt that extended 8,000 to 12,000 meters out from the Da Nang
Vital Area, the effective range of the enemy rockets. Within this circumference,
the 11th Marines instituted a central control system which included
the coverage by two artillery firing batteries of each part of the Da
Nang TAOR and the strategic placement of artillery observation posts
in the rocket belt. The infantry intensified its patrols and allied
aircraft increased their observation flights into and over the approaches
towards the most likely rocket-firing positions. At the same time, the
Marines imposed an 1800 to 0600 daily curfew on river and other waterway
traffic in the rocket belt area. Division psychological operations teams,
moreover, developed an extensive campaign among the local villagers
including money awards for information on the enemy rockets.13**

Despite all these efforts, the NVA rocket threat remained real. Unlike tube artillery, the rockets did not require a great deal of maintenance and they could be man-packed through the difficult terrain of western Quang Nam. Rocket launchers were considerably smaller than howitzers of a comparable caliber, and were thus much easier to conceal from U.S. air observers or reconnaissance patrols. Although mortars shared with rockets these traits of ease of maintenance, transportation, and concealment, the rockets had much greater range: the 122mm rocket could fire 12,000 meters, while the 140mm variety had a range of 8,900 meters. The 120mm mortar, on the other hand, could fire only 5,700 meters. Well-trained crews could assemble, aim, and launch their rockets in less than 30 minutes. In one attack on the Da Nang airfield, six enemy rocket teams fired 50 rounds within five minutes. With a few glaring exceptions, most of the enemy rocket attacks resulted in relatively little damage and few casualties. As Major General Raymond L. Murray, the deputy III MAF commander, observed, however, "it [the enemy rocket capability] was constantly on everyone's mind . . . ." With a relatively minor investment in men and

* Lieutenant Colonel Vincent J. Gentile, who commanded the 1st Tank Battalion at the time, recalled that most of his tank units were under the operational control of various infantry units. As commander of the Southern Sector, he controlled "a group of support unit headquarters elements south of Da Nang." As he remembered, "my impression is that we had more alerts than significant enemy activity in the SSDC." LtCol Vincent J. Gentile, Comments on draft, dtd 25Nov94 (Vietnam Comment File).

** Colonel John F. Barr, who served with the 11 th Marines and the
1st Field Artillery Group in 1967-68, observed that "rockers are still
the least expensive and most effective indirect fire weapon that a non-industrial
society can use." He stated that to counter the threat, the 1st Marine
Division established "an ad hoc "Rocket investigation Team,'" to gather
intelligence on enemy rocket tactics. This team consisted of a representative
of the G-2 or intelligence section, an artillery officer, a demolition
man, a photographer, and a security team provided by the 1st Reconnaissance
Battalion. At first light, after a rocket was launched, the team would
embark in a helicopter and would locate the firing site from the air
using coordinates provided by the 11th Marines. The team would then
land and "explore the site in detail." It would blow any rockets left
behind in place and take back any intelligence it was able to garner
about rocket tactics and firing sites. By various countermeasures, the
Marines reduced the amount of time that the enemy gunners had to mount
their attack. Colonel Barr commented that by late 1967, "every gun in
the 11th Marine Regiment, when not engaged in firing was pointed at
a possible rocket firing site .... The idea was to get as many rounds
in the air as soon as possible in order to disrupt rocket firing in
progress." Using a combination of visual sightings and sound azimuths,
the Marine gunners would try to identify "approximate site locations
through map triangulation. " Col John F. Barr, Comments on draft, dtd
26Oct94 (Vietnam Comment File).

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