The JASONs looked carefully at where Vietnamese insurgents might obtain tactical nuclear weapons (TNW) to respond to American nuclear first use, and how they might employ such weapons. 1n 1966, the Chinese had only recently tested and deployed their first nuclear weapons, so the JASONs considered the most likely source to be the former Soviet Union’s already well-stocked arsenal of tactical nuclear weapons.
Supply of Soviet Tactical Nuclear Weapons
The JASONs state that Soviet tactical missile and fighter and medium bomber delivery systems relied on “fairly heavy warheads” that suggested “yields in the multi-kiloton range for all systems.” (p. 32).
“The known Soviet TNW,” they state, “are all heavy and high-yield weapons designed for large-scale mechanized warfare. The smallest of them have warheads in the 1000 pound class, which would be extremely difficult for guerilla forces to handle.” (p.6). Thus, these standard Soviet TNW could only have been used in a direct riposte to US nuclear first use in Vietnam by the Soviets delivering them by aircraft, via missiles fired from offshore, or by sledding the weapons into a harbor base from offshore vessels.
They noted further that: “Very little seems to be known about the existence of TNW [tactical nuclear weapon] designed specifically for infantry” on the Soviet side (p. 31). They referred to a possible mortar or recoilless rifle-fired tactical nuclear weapons “weighing a few hundred pounds” as a “possible delivery system with a range of a few miles.”
The JASONS appear to have been uncertain as to whether the former Soviet Union had such weapons, assuming at one point that the USSR has manufactured a supply of TNW (p.31) “To give a feeling for what the Soviets might do along these lines,” they provided a Table that listed some relevant US systems, implying that physical design imperatives would lead the Soviets to make small tactical nuclear weapons along the same lines. These included nuclear warheads delivered by Little John missiles, Davy Crockett rocket fired from either a 120-mm or a 150-mm recoiless rifle, and Atomic Demolition Munitions. The latter came in three varieties, ADM50 and 50, and Special ADMs) (p.34). In reality, it appears that ADMs did not appear in the Soviet Arsenal until the 1970s. (Soviet Nuclear Weapons, p. 202). Indeed, the Soviet Union never developed or fielded a “recoiless rifle” similar to the Davy Crockett. As for the M-240 mm towed heavy mortar it was huge and heavy (3 tons) and not very portable. Ironically, it appears as though there weren’t really any Soviet “portable” weapons available in 1966 (Stan Norris, email, March 7, 2003). In a sense, the JASONs were shadow-boxing their own visualizations as to tactical nuclear weapons that might have been used by the Viet Cong, although at the time, there was no way to know what the Soviets or Chinese might have supplied.
Little John missiles used a W45 warhead with a yield of 1-10 kilotons. The Davy Crockett rocket used a W54-2 warhead with a yield of about 0.25 kiloton. Medium ADMs used W45-3 warheads with a 1-15 kiloton yield. Special ADMs used a W54 warhead with 0.1-1 kiloton yield. (U.S. Nuclear Forces and Capabilities, pp. 10, 33, 53, 60)
They noted that mortar tubes to fire nuclear weapons would weigh 500 to 1000 pounds, which would be “cumbersome for guerilla use.” (p. 33). “However,” they continued, “it is certainly within Soviet or Chinese technological capabilities to build sectioned mortar tubes, particularly since each tube need only be fired a few times, at most.” (ibid).
Moreover, “If sectioned barrels and lightweight projectiles (250-pound) are used, the approach and emplacement problems would not differ significantly from logistic problems now solved successfully by the VC [Viet Cong].” All in all, they asserted, “While the possibility of a FROG [Free Rocket Over Ground ] attack cannot be neglected, a more probable mode of attack is one with nuclear weapons fired from mortars or recoilless rifles.” (p. 36)
With reference to ADMs, they state: “Relatively little seems to be known about the existence of Soviet atomic demolition munitions (ADM). Since such devices are small and light in weight and are emplaced by hand, this may merely indicate a gap in intelligence. There is no doubt that the USSR is capable of either designing ADM or adapting weapons from stockpile to ADM with little difficulty.”
Delivery of Tactical Nuclear Weapons to Targets
The main emphasis in Soviet supply of TNW to Vietnamese insurgents, the JASONs suggested, would be on supplying the smaller weapons mentioned above into the battlefield. “In view of their small sizes and weights, introduction of these weapons into NVN [North Vietnam] and subsequent transportation along the Ho Chi Minh Trail into SVN [South Vietnam] offers only minimum difficulties, although it would probably take several months to deliver 50 to 100 weapons in this way.” (p. 38). Thus, a nuclear retaliation for US first use might take three-to-six months-a kind of slow motion nuclear war.
Types of Insurgent Counter-Attack
They examined three ways that insurgents might retaliate to US nuclear first use. The first was an intense barrage of 70-100 weapons of 10-20 kilotons in a coordinated attack on many US bases at once. “While such an attack cannot be ruled out,” they concluded, “it would require great coordination and run some risks of degradation by premature firing or partial discovery.” (p. 41).
They also reviewed a drawn-out, piecemeal attack by guerilla units over weeks or months. “Attacks of this kind are likely to include as much “mix” as the VC are capable of providing-mortar attack by infiltrating units and clandestine delivery by truck or boat.”
The JASONs considered a third type of “revenge” attack in which the Vietnamese were unable to launch a full-scale, tactical, nuclear counter-attack-particularly if they had to rely on presumably crude Chinese rather than Soviet nuclear weapons. In this attack scenario, they posited that the Vietnamese would use a few nuclear weapons of moderate yield to attack very important targets. They judged Saigon airport to be the most attractive single target in Vietnam: “The airport is on the outskirts of Saigon, in an area of sufficiently low population density to qualify as a military target, and the usual wind conditions would not carry fallout directly over Saigon. The present level of security would not keep out suitcase bombs.” (p. 41).
Finally, they calculate that the 14 main US bases in Vietnam could be divided into subunits requiring one or two 10-kiloton airbursts for more or less complete destruction, presenting a total of about 70 targets and a requirement for about 150 10 kiloton weapons (allowing for duds, capture, redundant use etc). Although this number of weapons was well beyond Chinese stockpiles in 1966, this was not so with respect to the Soviet nuclear arsenal. “Thus,” they conclude, “there are no stockpile limitations and probably no weapon limitations on repeated attacks on U.S. forces with Soviet-supplied TNW.” (p. 45).
US Tactical Nuclear Weapons Considered by JASONS For Use in Vietnam
In considering American nuclear first use against the Vietnamese, the JASONs referred mostly to gravity bombs using either airburst or groundburst. (for example, p. 11). They did not seem to consider using other US tactical nuclear weapons such as ADMs, nuclear artillery shells, or other short and medium-range missile-delivered warheads. Gravity bombs would likely have been delivered from aircraft carriers operating offshore which would minimize the risk of loss-of-control of weapons on the ground. The carrier-launched A4 Skyhawk, for example, could deliver a single B28 (about a 20 kilotons), B43 (1 megaton), B57 (5-10 kiloton), or B61 (100-500 kiloton) warheads. (U.S. Nuclear Forces and Capabilities, pp. 44, 49, 63, 65).
Citing 1966 studies by Sandia Corporation, the JASON’s refer to a “research earth borer” (REB) tactical nuclear weapon under development “which is an airdropped bomb that penetrates the ground to a desired depth. The bomb is optimized for a particular yield, and the crater diameter is about double that of a surface-burst of the same yield. Alternatively, the depth can be chosen so that the explosion is almost contained and fallout practically eliminated. [next sentence deleted by security exemption]” (p. 11).
“REB,” the JASONs stated, “would be a useful weapon for dealing with the deep VC tunnel systems. The destructive range would not be much increased over that of a surfaceburst, so that a large number of weapons and accurate location of targets would still be needed. Elimination of long-range fallout, if REB actually performs up to specifications, would make a nuclear attack on tunnel HQ a relatively inconspicuous operation.”
However, this weapon was not yet in service (indeed, it is still not in service although a variant of the B61 bomb has been created that placed a hardened steel casing around the warhead to enable it to penetrate about 20 feet into dry earth when dropped from 40,000 feet).
Page references are to: F.J. Dyson, R. Gomer, S. Weinberg, S.C. Wright, Tactical Nuclear Weapons in Southeast Asia, Study S-266, JASON Division, Institute of Defense Analysis, contract DAHC15 67 C 0011, published March 1967; released to Nautilus Institute on December 4, 2003.
Other technical specifications of US and Soviet tactical nuclear weapons are from:
T. Cochran et al., US Nuclear Forces and Capabilities, Nuclear Weapons Databook, volume 1, Ballinger, Cambridge, Massachusetts, 1984.
T. Cochran et al., Soviet Nuclear Weapons, Nuclear Weapons Databook, volume 4, Natural Resources Defense Council, Washington DC, 1989.