Despite the hundreds of thousands of tons of bombs that were dropped on Mu Gia and other strategic sections of the Ho Chi Minh trail, the Rolling Thunder campaign begun in March 1965 failed in its interdiction objectives for reasons that are still debated by military historians. As early as the summer of 1966, internal review and mounting congressional and public pressure to find coercive leverage over North Vietnam led to a reevaluation of the bombing strategy.
It was against this backdrop of frustration over the inability to interdict the Trail that the possibility of employing nuclear weapons was discussed in Pentagon circles. The JASON study was a response to this loose talk and, although it did not specifically focus on Mu Gia pass, it did analyze interdiction of the Ho Chi Minh trail, including nuclear attacks on bottlenecks such as Mu Gia pass.
The JASONs argued that tactical nuclear weapons (TNW) would be most effective in stopping the enemy from moving “large masses of men in concentrated formations,” against fixed and accurately located targets like bridges, airfields, and missile sites — conditions that were radically different from those that existed along the Ho Chi Minh trail.
Moreover, although they conceded that the use of TNW for interdiction of lines of communication in North Vietnam could be effective under certain circumstances, they determined that it would have required a “huge number of weapons.” Using evidence from a RAND targeting study, which indicated that one TNW equaled on average about 12 non-nuclear attack sorties, they estimated that a completely nuclear Rolling Thunder campaign would have required about 3000 TNW per year. They concluded that such an attack would eventually result in a stalemate, “with the enemy forces retiring into the forests and the US nuclear bombardment running into the law of diminishing returns.”
The JASONs did address the use of TNW to interdict passes in a generic fashion. They stated:
“TNW can be used for interdiction of passes and trails, independently of tree blowdown–Effects of blast, heat, and fire will only be felt by men who happen to be on the trails at the time of the burst; these effects are subject to [certain troop target] limitations. In conclusion, it appears that the interdiction of passes and trails by TNW can be effective only against massive enemy movements on a short time scale, but not against dispersed movements extending over many months or years.”
Balancing the moderate strategic advantages against what they characterized as the “catastrophic” political effects of TNW in Southeast Asia, the authors of the study concluded that the military advantages of unilateral use of nuclear weapons “are not overwhelming enough to ensure termination of the war, and they are therefore heavily outweighed by the disadvantages of eventual bilateral use.”