From Chapter 10, "Untying the Knot"
[pp. 193-195]
...McNamara's second Draft Presidential Memorandum on strategic forces, dated November 21, 1962, announced that the purpose of U.S. nuclear forces was "first, to provide the United States with a secure, protected retaliatory force able to survive any attack within enemy capabilities and capable of striking back and destroying Soviet urban society, if necessary, in a controlled and deliberate way." Its secondary purpose was "limiting damage," that is, " to deny the enemy the prospect of achieving a military victory by attacking our forces."
McNamara's post-Cuba concern with deterring nuclear war was also evident: "The forces I am recommending give any rational Soviet decisionmaker the strongest possible incentives to avoid nuclear attack on ourselves or our allies."[17]
[Alain] Enthoven proceeded to get to work defining the new first goal, deterrence.[18] If the strategic forces' role was that of "striking back and destroying Soviet urban society...in a controlled and deliberate way," how much force was enough?
Enthoven and staffer Frank Trinkl designed a computer program enacting a retaliatory attack that dropped one-megaton warheads on Soviet cities and burst aboveground to destroy buildings and people. Only those killed and wounded immediately were counted as casualties; long-term casualties due to fallout were not included. Their computer calculated the damage achieved by different levels of attack. Thus the number of delivered megatons could be correlated with the percent of Soviet population and industrial floorspace destroyed.
Enthoven knew that in reality, with SIOP-63, the new operational war plan, the vast majority of U.S. nuclear weapons were targeted on Soviet military forces, with only 18 percent aimed at cities and industry. But he decided that this model was valid anyway. As McNamara said in his 1963 Draft Presidential Memorandum, "The calculations [of attacks on Soviet cities and industry] are our best estimates of the results of possible Soviet calculations of what we could do to them in retaliation if they were to attack us."[19]
Enthoven's computer program generated two curves. One showed the percentage of industrial floorspace destroyed, and the other the percentage of population harmed. Both were computed as a function of how many megatons were delivered on these two kinds of targets.[20]
Both curves rose sharply as the number of megatons increased. Both then bent and became nearly horizontal, meaning that above certain levels of megatonnage, relatively fewer additional people or industrial targets would be destroyed. The bends, or "knees," in the curves fell at roughly 400 megatons; if 800 megatons were delivered, only 10 percent more people and 3 percent more industry would be destroyed, for example.
But the bends in the curves were approximate. They could have picked 150 megatons as a yardstick of sufficiency because 150 megatons would destroy 60 percent of industry and 15 percent of population. Or they could have picked 500 megatons, which would eliminate 70 percent of industry and 35 percent of population. At 400 delivered megatons, one third of the Soviet population and half of Soviet industry would be wiped out.
Enthoven and Trinkl presumed, of course, that their adversary would be rational, although history does not necessarily bear out this assumption. Many a national leader has launched into war deluding himself that the fatalities on his own side will be low and that the war will be short. On the other hand, since no leader has yet started a nuclear war, perhaps calculations of impending deaths do deter.
....Four hundred delivered megatons became the yardstick for the amount of damage that should deter the other side from starting a nuclear war.[21] But McNamara and Kennedy were buying 656 Polaris missiles and 1,200 land-based ICBMs and already had thousands of megatons that could be delivered by bombers.
McNamara and Enthoven then tripled the yardstick. They adopted a conservative assumption: that any of the three "legs" of the force -- bombers, land-based missiles, and sea-based missiles -- should be capable of the Assured Destruction mission alone. In this way they rationalized their larger force.
Analysis had given them a chance to cut the size of the programmed force by two thirds, but they never seriously considered doing so. The implications of the overwhelming U.S. superiority for a possible reduction of U.S. forces were simply not considered closely. McNamara had pushed the enormous buildup in his first year in office; he was wedded to it. In 1963 he was not yet a revolutionary advocate of deep nuclear force cuts.
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[pp. 193-195]
...McNamara's second Draft Presidential Memorandum on strategic forces, dated November 21, 1962, announced that the purpose of U.S. nuclear forces was "first, to provide the United States with a secure, protected retaliatory force able to survive any attack within enemy capabilities and capable of striking back and destroying Soviet urban society, if necessary, in a controlled and deliberate way." Its secondary purpose was "limiting damage," that is, " to deny the enemy the prospect of achieving a military victory by attacking our forces."
McNamara's post-Cuba concern with deterring nuclear war was also evident: "The forces I am recommending give any rational Soviet decisionmaker the strongest possible incentives to avoid nuclear attack on ourselves or our allies."[17]
[Alain] Enthoven proceeded to get to work defining the new first goal, deterrence.[18] If the strategic forces' role was that of "striking back and destroying Soviet urban society...in a controlled and deliberate way," how much force was enough?
Enthoven and staffer Frank Trinkl designed a computer program enacting a retaliatory attack that dropped one-megaton warheads on Soviet cities and burst aboveground to destroy buildings and people. Only those killed and wounded immediately were counted as casualties; long-term casualties due to fallout were not included. Their computer calculated the damage achieved by different levels of attack. Thus the number of delivered megatons could be correlated with the percent of Soviet population and industrial floorspace destroyed.
Enthoven knew that in reality, with SIOP-63, the new operational war plan, the vast majority of U.S. nuclear weapons were targeted on Soviet military forces, with only 18 percent aimed at cities and industry. But he decided that this model was valid anyway. As McNamara said in his 1963 Draft Presidential Memorandum, "The calculations [of attacks on Soviet cities and industry] are our best estimates of the results of possible Soviet calculations of what we could do to them in retaliation if they were to attack us."[19]
Enthoven's computer program generated two curves. One showed the percentage of industrial floorspace destroyed, and the other the percentage of population harmed. Both were computed as a function of how many megatons were delivered on these two kinds of targets.[20]
Both curves rose sharply as the number of megatons increased. Both then bent and became nearly horizontal, meaning that above certain levels of megatonnage, relatively fewer additional people or industrial targets would be destroyed. The bends, or "knees," in the curves fell at roughly 400 megatons; if 800 megatons were delivered, only 10 percent more people and 3 percent more industry would be destroyed, for example.
But the bends in the curves were approximate. They could have picked 150 megatons as a yardstick of sufficiency because 150 megatons would destroy 60 percent of industry and 15 percent of population. Or they could have picked 500 megatons, which would eliminate 70 percent of industry and 35 percent of population. At 400 delivered megatons, one third of the Soviet population and half of Soviet industry would be wiped out.
Enthoven and Trinkl presumed, of course, that their adversary would be rational, although history does not necessarily bear out this assumption. Many a national leader has launched into war deluding himself that the fatalities on his own side will be low and that the war will be short. On the other hand, since no leader has yet started a nuclear war, perhaps calculations of impending deaths do deter.
....Four hundred delivered megatons became the yardstick for the amount of damage that should deter the other side from starting a nuclear war.[21] But McNamara and Kennedy were buying 656 Polaris missiles and 1,200 land-based ICBMs and already had thousands of megatons that could be delivered by bombers.
McNamara and Enthoven then tripled the yardstick. They adopted a conservative assumption: that any of the three "legs" of the force -- bombers, land-based missiles, and sea-based missiles -- should be capable of the Assured Destruction mission alone. In this way they rationalized their larger force.
Analysis had given them a chance to cut the size of the programmed force by two thirds, but they never seriously considered doing so. The implications of the overwhelming U.S. superiority for a possible reduction of U.S. forces were simply not considered closely. McNamara had pushed the enormous buildup in his first year in office; he was wedded to it. In 1963 he was not yet a revolutionary advocate of deep nuclear force cuts.
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[17] DPM, November 21, 1962.
[18] Kaplan, Wizards, 316ff.
[19] RSM, "Draft Memorandum for the President," December 6, 1963, p. I-5.
[20] The chart is sketched at Kaplan, Wizards, 318.
[21] The yardstick of 400 megatons was not original with Enthoven in 1963. Before the ICBM was even built, one of its developers computed the likely future "sufficient" force. C. W. Sherwin, chief scientist of the Air Force, picked up an analysis by Warren Amster of Convair Corporation, an Air Force contractor on the ICBM program, that 300 to 400 missiles could deter. Sherwin publicized this prescient conclusion in "Securing Peace Through Military Technology," Bulletin of the Atomic Scientists 12, no. 5 (May 1956): 159-165. Amster's view was published in the same issue of Bulletin of the Atomic Scientists, "Design for Deterrence," 164, 165. Discussed at Freedman, The Evolution of Nuclear Strategy, 191, 192. The WSEG-50 study, on which RSM was briefed in 1961, proposed that 200 to 300 survivable Polaris missiles would be sufficient. Therefore, Enthoven's conclusion that 400 delivered megatons, or 200 survivable missiles, was enough reflected a consensus.
