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He was, of course, referring to the monster thermonuclear device exploded by the U.S.S.R. during its 1961 test series. Said McNamara: "They have demonstrated a device of 60 megatons which we believe could be weaponized at about 100 megatons. The Soviets probably have no missile at this time which will deliver a 100-megaton warhead." As to that, some U.S. scientists and military leaders disagree with McNamara, believe that the 100-megaton giant, weighing between 20,000 and 30,000 Ibs., could already be hung on the end of the Soviets' gigantic Vos-tok-launching rocket, nicknamed "The Beast" by U.S. intelligence agents, and fired with reasonable accuracy over 3,500 miles.
McNamara, while admitting that the treaty, by barring atmospheric testing, would prevent the U.S. from developing a 100-megaton bomb, told the Senators that without any testing the U.S. "can develop a warhead with a yield of 50 to 60 megatons for a B-52 delivery," and with underground tests could develop "a 35-megaton warhead for Titan II."
In any event, Secretary McNamara does not believe that the U.S. arsenal requires a superbomb. Said he: "One possible use of the very high-yield weapons would be to deliver them by missile and detonate them at altitudes of 100,000 feet and above, presumably over cities. Detonation at such altitudes could cause significant thermal damage—fire—over hundreds of square miles. But a better way to achieve even greater destruction, and a way which is within the present U.S. capabilities, is to divide the attack among several smaller weapons so as to saturate any defenses."
Doubling the Megaton. The U.S. is —and has been for several years—committed to such "saturation" strategy. In its simplest terms, this means avoiding reliance on a few huge bombs, peppering an enemy nation with hundreds of relatively small ones. Since devastation does not increase arithmetically with megaton power, two 10-megaton warheads properly placed can do almost as much damage as one 100-megaton giant. The Pentagon goes under the assumption that accuracy—even in saturation—is the key to success, that if a missile's accuracy is bettered by 20%, it is equivalent to doubling the megaton force of the warhead. This can be done without nuclear tests of any kind.
Concluding his criticism of a strategy which would depend on superbombs, McNamara said: "Very high-yield warheads are relatively inferior as second-strike retaliation weapons; it is much more difficult and costly to make them survivable—to harden, camouflage or make mobile the huge missiles required to deliver these weapons."
Survival Silos. A "second-strike retaliation weapon," such as Minuteman or Polaris, must be able to withstand enemy attack, and have all its intricate systems, including communications, intact when the pounding is over. Said McNamara: "Our missile force is deployed so as to assure that under any conceivable Soviet first strike, a substantial portion of it would remain in firing condition. Most of the land-based portion of the force has been hardened as well as dispersed."