Losing Vietnam (36 page)

Figure 7. Locations of Khmer Communist Attacks by Fire on Mekong River Convoys. (Source: USSAG briefing, “Analysis of Mekong Convoy Security,” 22 March 1974, Headquarters USSAG, Nakhon Phanom, Thailand.)

Next we asked what the nature of the attacks was. Crews could tell
the weapons utilized in 102 of the 140 attacks on convoys. Normally, multiple weapons were fired, and the 75 mm recoilless rifle was the predominant attack weapon—utilized in over 53 percent of the identified attacks—with rocket-propelled grenades being a secondary means of attack.
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The B-40 and B-41 rocket-propelled grenades' range made them effective in the dry season, when the river was narrow. However, the recoilless rifles could be effective all year around. In South Vietnam, my unit, the 9th Infantry Division, had encountered these weapons, which the enemy effectively used against defensive positions since its penetration capabilities were great. We made the weapons ineffective by erecting in front of our positions simple chain-link fences. Incoming rounds detonated on the fences and spent their lethal penetrating cores before they struck the defensive positions. Obviously, this was a solution to the communists' most destructive weapons. And
sandbags could effectively protect against machine guns, small arms, and mortars.

Figure 8. Height of Mekong River and Attack Rate. (Source: Headquarters USSAG, Nakhon Phanom, Thailand.)

Many advocated small convoys as the method to transit because the naval escort vessels could concentrate on protecting only a few vessels instead of being spread out along the length of a large convoy. Analysis of the data, however, indicated that except for the very small convoys of three vessels or fewer, and the very large, nineteen vessels or more (for which we had data on only one convoy), convoy size made no difference.

A debrief of the Cambodian naval escorts and the captains of the tugs and vessels indicated that the KC had built entrenched locations at choke points from which they attacked and that the attacks had a set pattern. As the convoy passed the enemy interdiction location, all of its positions would open fire simultaneously, each concentrating on a single vessel. Since not every enemy position had recoilless rifles or rocket-propelled grenades, this meant that only a few vessels were subject to lethal fire.
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In summary, to increase convoy security the Cambodians must position troops at known attack locations, use aircraft and artillery to suppress fire, consider travel at night, and use sandbags, sheet metal, and fencing to protect vessels and cargo. In general, each convoy required the same security efforts. Attacks by fire were a function of the number of convoys and generally not of the number of vessels in the convoy.
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Therefore, the tonnage per convoy must be increased. Already in December, 67,006 metric tons were shipped, doubling the sizes of previous rice and ammo shipments.

To counter enemy threats, FANK implemented its Mekong Special Zone Plan, which had five main components: troop dispositions, artillery, air support, riverine protection, and overall coordination.
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Thirty-two tubes of artillery provided coverage over the complete length of the Mekong in Cambodia. To coordinate these artillery units, the joint staff established a fire support coordination center at the Mekong Special Zone headquarters in Neak Luong. In all, FANK provided the equivalent of twenty-eight battalions on the Lower Mekong. The air force flew missions to provide continuous air cover and utilized tactical air strikes when available.

On the Lower Mekong, the navy had sixty-five vessels operating.
MNK briefed convoy security at the pre-sailing conference in Tan Chau, South Vietnam. The navy was responsible for coordinating convoy security, and it did a systematically effective job. Once the convoy was under way, to maintain communications security after the pre-sail conference, the navy passed a message to all concerned, citing frequencies and check point locations.

With my idea of standoff fencing, which could be installed relatively cheaply and expeditiously, headquarters USSAG developed a plan for protecting ammo barges, and on 8 December 1973 we forwarded the plan to the Military Sealift Command, Far East, in Yokohama, Japan.
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It called for standoff fencing to protect against rocket-propelled grenades and recoilless rifles.

While watching the unloading of ammunition barges at Phnom Penh, I noted that the multiple layers of sandbag protection that had been placed on top of the ammo created major unloading problems, since the sandbags took a considerable amount of time to remove and often split, causing additional problems. It was important to reduce the turnaround time, since the dock area was relatively unprotected. Analysis of major attack positions along the Mekong indicated that the enemy usually fired at the ammo barges from an elevation of two meters or less and at a distance of three hundred to eight hundred meters. The slight angle of incidence to the top of the barge resulted in a flat trajectory. Therefore, I recommended using sheet steel for overhead protection, which would ensure ricochets and would be easier to both emplace and remove with cargo-handling equipment. Such covering could be easily stored and would reduce the net weight of protective material, thus increasing the ammo storage capacity.

Subsequently, to increase the chain-link standoff distance and enable more ammo cargo per barge, we recommended the use of shield barges, which would be towed alongside the ammo barges. This created much static for many reasons; most predominantly, some supposed that it would slow the tugs' advance. Regardless, we prevailed, and four deck cargo barges were outfitted for a trial run (see
photo 6
).

Meanwhile, on 18 February 1974, northbound convoy TP-71 was attacked and the ammunition barge
Mt. Hood
was hit by recoilless rifle and machine gun fire and sank, taking with it 1,097 metric tons of ammo. This unfortunate incident gave great impetus to the protective barge project.

Photo 6. Barge Protection on the Mekong River. (Source: Headquarters USSAG, Nakhon Phanom, Thailand, produced by 432nd Reconnaissance Technical Squadron, U.S. Air Force.)

Investigations had determined that the most suitable support system for the proposed standoff protection system was the deck cargo barges in the ARVN watercraft fleet. To facilitate the project, the South Vietnamese cooperated fully and arranged immediately for the transfer of fourteen barges.
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The first four shield barges were completed in early March and tested on 6–7 March, with excellent results. However, several of the tug masters believed that with the shields protecting the ammo barges, the tugs themselves would become targets. They also cited their potential loss of maneuvering capability, should a barge part a line or have any other problems. The tug masters changed their tune once they actually used the shield-barge concept. Mr. Benito Cirera, the master of the motorized tug
Polaris
, wrote, “In the opinion of the undersigned the shield barges is a commendable if not magnificent improvement to our present securing arrangement.”
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The enemy attack against TP-84 on 24 May 1974 provided the first opportunity to measure the escort barge concept's effectiveness at protecting critical ammunition cargo. One of the seven screen barges took three hits. One round created a ten-by-five-foot hole, another a basketball-sized hole, and the third ricocheted off. The ammo remained undamaged.

It took several months to put our recommended convoy procedures in place, but by March 1974 we had procured the screen barges and limited the convoys to four sailings per month, but with many more vessels per convoy. The MNK had their riverine procedures working, and marine battalions occupied several of the key choke points. However, the plan required at least three additional marine battalions. The navy generally supported each convoy with twenty to thirty vessels. Yet, on some occasions the employment of navy vessels was less than optimum, and upgrading was needed. The number of sorties flown in support of the convoys increased greatly. The air force's ability to strike threat areas and react to attacks was much improved. The fire support coordination center improved artillery effectiveness, facilitating artillery employment against targets of opportunity.

In spite of all the improvements, there were still several areas of concern. To ensure maximum utilization of assets, the Seventh Air Force flew reconnaissance flights during convoys and analyzed the results. The use of large numbers of small and sometimes underpowered rice
vessels was a major problem; over the previous several months USAID had chartered such vessels to transport rice and grain to Phnom Penh. These vessels stretched out convoy lengths; photographs show one convoy in excess of twenty kilometers.
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Discipline materially degraded when the convoys extended over great distances, severely straining both naval and air force assets. Lately, the enemy had been able to pick and choose its attack times almost free from countermeasures. Convoy vessel crews had been used to at least a one-to-one relationship between naval and commodity vessels, and they were unhappy. Therefore, to improve convoy security the tripartite deputies imposed a ceiling of twenty powered vessels per convoy, with each vessel having an over-ground speed of at least three knots. The forthcoming flood season—when the Mekong currents would increase from one knot between December and June to two knots in July–August, and to three or four knots in September–November—would only exacerbate the problem with the small, underpowered rice vessels.
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Notwithstanding the rice vessel problems, a review of convoy statistics indicated that there had been significant improvement when comparing the dry-season periods of the improved Mekong security—that is, March through June 1974 with the same period in 1973. In 1973 there were 208 transits, carrying 176,516 short tons, and forty-nine vessels were hit, including eight sunk and four beached. In 1974 there were 530 transits, carrying 300,732 short tons, and forty-five vessels were hit, with only one beaching.

The
Bonanza III
, part of TP-88, carrying two thousand metric tons of rice, received a grenade round in its engine room, which caused a fire, and thus on 28 June 1974 the vessel was beached at Peam Chor, losing its cargo. Although only 8 percent of the vessels in the 1974 period were hit, as compared to 24 percent in the 1973 period, the Phnom Penh run was still very dangerous. In both years four crew members were killed. Running the enemy's gauntlet of fire took great courage. However, in the 1974 period there were no SCOOT ammo tug casualties.

By early summer, the Phnom Penh stockage objectives for rice, petroleum, and ammunition had been met, and analysis indicated that either three or four convoys per month, consisting, respectively, of nineteen or fourteen vessels per convoy, could meet necessary stock replenishment requirements.

Without a doubt, the major convoy problem area was the lack of security provided by the Khmer Navy. In the early days the SCOOT program had a goal to transport two thousand metric tons per month. In those days, each tug could be protected by several river patrol boats. However, as the war increased in intensity and refugees by the hundreds of thousands fled to Phnom Penh, the requirements for ammo, rice, and petroleum increased greatly, necessitating more vessels to be protected by the same military assets. The navy and air force assets, consequently, were spread thin, and the convoy crews became disenchanted. But the navy's tactics also left much to be desired, since the navy would not aggressively counter the enemy attacks. Further, the marines were not sweeping the ground at the hot spots. Starting in June 1974, complaints from ship masters began to surface.
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On 14 December the vice president of SEAPAC Inc. wrote: “As much as the tug officers and crew are aware that it is part of the deal to be fired upon, although this is not stipulated in the Service Agreement in so many words, they also know that they are supposed to be provided with sufficient military protection. The protections they are afforded, are inadequate and not properly executed.” Others stated, “To continue in this work under the present circumstances is the height of recklessness.” They wanted reassurance, or else they would withdraw their assets from the program.
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