The VC and the NVA used their improvised rocket artillery with deadly effect.
North Vietnamese Army weaponry underwent a dramatic shift during the time I commanded the Combined Materiel Exploitation Center (CMEC), between August 1965 and September 1968. Headquartered at the Tan Son Nhut airbase, the center worked to identify any new enemy weapons and analyze their implications in terms of tactical requirements and political intelligence.
While I was there, new types of rockets increased the NVA firing range from 2 miles to about 6 miles, a development that not only gave clear evidence of a dramatic increase in Soviet arms support to the North Vietnam ese but also spurred immediate changes in U.S. and ARVN defense tactics.
In the early stages of American involvement in Vietnam, Viet Cong forces were armed with a hodgepodge of light infantry weapons. Some were homemade, while others were captured from the French, seized from the Japanese World War II occupation forces or furnished by Chinese Communists from their supplies of American weapons captured in Korea. The heaviest weapons were a few 60mm and 81mm mortars, and a sprinkling of 57mm and 75mm recoilless rifles.
This all changed with the intervention of NVA regular units in the fall of 1965. The combined NVA and VC forces, however, demonstrated very little artillery capability until they unleashed a surprise rocket attack on Da Nang Air Base on February 27, 1967. During the attack, they fired more than 100 140mm rockets from launcher tubes fastened to wooden planks. They were grossly inaccurate and caused very little actual damage, but the psychological impact was severe. Several of the unfired rockets and launcher tubes were recovered; examination of the tubes indicated that they probably had been disassembled from Soviet BM-14 truck-mounted, multitube rocket launchers.
A week later, on March 6, the NVA launched a much more serious rocket attack against Camp Carroll near the DMZ. That attack caused some casualties and considerable damage to equipment. Personnel from the CMEC and Marine Explosives Ordnance Disposal (EOD) were unable to positively identify the incoming projectiles because no launcher tubes, unfired rockets or duds were recovered. Analysis of available fragments, however, revealed pieces of spring-loaded folding fins and numerous chunks of stamped, embossed sheet-metal fragmentation liner. Since the standard 140mm rocket was spin-stabilized by canted nozzles and had no fragmentation liner, the new rockets were obviously something different. The CMEC report concluded only: “Unidentified rockets of unknown origin, approximately 115mm to 132mm in diameter.”
The significant upgrading of NVA and VC rocket capability was not a complete surprise to the intelligence community. There had been vague indications from captured enemy documents and prisoner interrogation reports that new weapons were coming.
Late in 1966, two Studies and Observations Group (SOG) NCOs returning from a deep penetration mission in Laos gave CMEC samples of a previously unknown Soviet fuze, which turned out to be the DKZ-B. Evaluation showed that the fuze was structurally similar to the Soviet GVMZ-7 fuze for the 120mm mor tar. But the DKZB fuze had a centrifugal, bore-riding safe ty feature and a delay pellet for spin-stabilization. That meant the projectile was fired from a tube with rifling.
At CMEC we realized that the previously unknown fuze found in enemy ammunition caches in eastern Laos meant that a new weapon would soon appear on the South Vietnamese battlefield. But for the moment, all we could do was wait for the other shoe to drop. Enemy rockets meanwhile continued to hit friendly base areas, and two more rocket types were identified. The Chinese 102mm rocket was a reduced version of the American World War II 4.5-inch barrage rocket. The Chinese version, along with the Chinese 107mm Type 63 rocket, had first made their appearances during the Korean War. Both were spin-stabilized, light and easy to transport, and their design made field expedient launching relatively simple.
My personal introduction to the 102mm rocket came when one of these hit the apron in front of the large, French-built hangar directly behind our CMEC building at Tan Son Nhut. A second rocket pierced the hangar roof, but it failed to explode. Of all the enemy rockets fired, that was the only known dud.
A VC rocket attack on Bien Hoa Air Base on May 12, 1967, caused only moderate damage but provided a major breakthrough. An AC-47 on station at the time forced the VC to abort their attack and abandon some equipment. An ARVN reaction unit recovered our first 122mm rocket, complete with a DKZ-B fuze. It was a conventional, spin and fin stabilized rocket, with one odd feature—a small stud and roller screwed into the rocket motor, just ahead of the tail fin and canted nozzle section. We did not understand its purpose until a 122mm launcher was captured later. The stud and roller device rode in a covered spiral slot in the launcher tube, which imparted a strong, clockwise spin to the rocket as it traveled up the tube.
That mechanical device to increase the accuracy of an inherently inaccurate rocket provided the key to identifying the origin of the 122mm rocket/launcher combination. The same covered spiral slot was visible in high resolution photos of certain Soviet vehicles. That meant that the launcher tubes had been disassembled from Soviet truck-mounted, 40-tube BM-21 multiple rocket launchers, first identified in Soviet units in 1964.
The shortened single-launch tube was mounted on a simple ground tripod. According to captured documents and prisoner interrogations, VC rocket teams usually traveled by water, using locally available sampans. Two men carried the launcher tube and one carried the tripod. Each rocket was broken down into two loads to facilitate handling, using the original Soviet wooden shipping boxes.
As the frequency of the rocket attacks increased, we saw that NVA and VC rocket teams often used field expedient methods to launch them, especially in the case of the smaller, lighter Chinese 107mm Type 63 rocket. MACV intelligence tasked CMEC to try to duplicate these launching systems.
Marine Chief Warrant Officer Thomas Swearengen, an EOD specialist, was able to rig and fire some 80 captured rockets of various calibers, from both field expedient and factory-built launchers. The test firings, conducted both in the afternoon and in the early evening, were filmed for the training of aircraft crews in the identification and reporting of rocket launchings. It is virtually impossible to determine the caliber of the rocket by looking at the launching back blast from the air.
Between September 1968 and the withdrawal of American combat units in 1973, many additional variations of the enemy rockets appeared. Some rockets were fitted with oversize warheads, which greatly reduced their range. Some were fitted with range-retarding disks, called Malandrin Disks—a simple, sheet metal collar placed between the fuze and the projectile—which increased air drag, thereby making it possible to fire from shorter ranges.
The enemy showed ingenuity and expertise in modifying rockets and other weaponry during the war. Many examples of the modified rockets are on display and open to the public at the U.S. Army Ordnance Museum at Aberdeen Proving Grounds in Maryland.
Originally published in the August 2008 issue of Vietnam Magazine. To subscribe, click here.