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The rest—over 7,000 warheads—are "strategic," built to travel thousands of miles and explode deep in enemy homelands. They are perched in the nose cones of intercontinental missiles or snugly enclosed in bomb casings aboard long-range aircraft. McNamara told the Senate group that "in the past 24 months alone, there has been a 100% increase in the number of nuclear warheads in the strategic alert forces." He said that the "megatonnage" of the force had "more than doubled"—which is pretty impressive, considering that a single megaton equals the explosive power of 1,000,000 tons of TNT.
The Big Punch. America's strategic alert force—missiles, bombers and Polaris-armed submarines—is loaded with AP multimegaton warheads. The atomic arsenal currently includes:
> 126 Atlas missiles with 5-mega-ton warheads.
> 68 Titan missiles with 10-mega-ton packages.
> 150 flashy new Minutemen (two-thirds of them installed in the last six months, with 800 more to come within two years) with 800-kiloton warheads.
>144 Polaris missiles with 800-kiloton warheads on nine submarines at sea (with 32 more subs and 512 more missiles by 1968).
> 400 Hound Dog air-to-ground missiles with 1-megaton warheads.
In addition to these, the strategic force has 2,000 10-megaton bombs for delivery by its 720 old, slow B-47 bombers and its 80 new supersonic B-58s. The biggest operative punch in the U.S. -arsenal—a 24-megaton bomb—is carried by the 630 SAC B-52s.
Such a bomb dropped over a large city would instantly burst into a fireball about four miles in diameter, start fires 40 miles away, open a crater a mile wide and hundreds of feet deep. It would puff a gigantic poisonous cloud of radioactive dust 25 miles into the sky, rain down enough fatal debris to kill humans more than 350 miles from the blast center. The U.S. has something like 1,600 such bombs ready for delivery by its B-52s.
In his testimony, McNamara pointed out that the U.S. always has a certain number of nuclear-armed bombers in the air, ready to head for enemy targets in the event of an attack on the U.S. Beyond these, said McNamara, there are "over 500 SAC bombers on quick-reaction alert"—a term meaning that they can be in the air within 15 minutes after receiving a warning that an attack is imminent. Continued McNamara: "Today the Soviets could place less than half as many bombers over North America on a first strike; the Soviets are estimated to have today only a fraction as many ICBM missiles, and their submarine-launched ballistic missiles are shortrange, require surface launch, and generally are not comparable to our Polaris force. Between now and 1966, it is estimated that our ballistic missile superiority will increase both absolutely and relatively."
Power-Package. McNamara devoted a considerable share of his calmly-delivered, matter-of-fact statement to discussing "yield-to-weight ratios." This involves putting the greatest possible destructive power into the smallest, most easily transportable package. Said McNamara: "The Soviet Union appears to be technologically more advanced than we are in the high-yield range, in the tens of megatons."