The Shield That Provokes
Robert McNamara, Alexei Kosygin, and the Anti-Ballistic Missile Paradox
Across the polished mahogany luncheon table inside the nineteenth-century Hollybush mansion at Glassboro State College in southern New Jersey on June 23, 1967, Soviet Premier Alexei Kosygin grew visibly agitated. Sitting opposite President Lyndon B. Johnson and Secretary of Defense Robert S. McNamara during the first day of the Glassboro Summit, the veteran Soviet head of government had just listened to McNamara demand that Moscow halt construction of its new Galosh anti-ballistic missile (ABM) ring around the Soviet capital. Flushing red and striking the table with his hand, Kosygin delivered a lecture grounded in two millennia of human moral intuition: defense is moral; offense is immoral. When a state builds a shield to intercept incoming warheads and save the lives of its mothers and children, Kosygin insisted, no sane person could call that an aggressive act or a threat to world peace.
Seated beside Johnson with his characteristic yellow legal pads filled with warhead survivability tables and cost-exchange ratios, McNamara did not dispute Kosygin's moral premise. Instead, the former Ford Motor Company president walked the Soviet delegation through the cold arithmetic of why, inside a thermonuclear duopoly, building a defensive shield is the most dangerous offensive provocation one superpower can commit against another.
By the mid-1960s, the United States and the Soviet Union had entered a strategic regime where neither side could intercept a full-scale attack launched by submarine-launched ballistic missiles (SLBMs) and hardened Minuteman or SS-9 intercontinental silos. Peace rested on the stability of Mutual Assured Destruction (MAD): even if Country A launched a surprise first strike that destroyed ninety percent of Country B's land-based bombers and silos, Country B's surviving ten percent of submarines and missiles would still penetrate Country A's undefended skies and incinerate fifty million people within thirty minutes. Because the guaranteed cost of retaliation exceeded any conceivable political prize, the finger stayed off the button.
McNamara demonstrated to Kosygin that introducing an anti-ballistic missile shield around cities immediately inverted four structural variables of that deterrence machine:
- * First-Strike Insulation: A nuclear missile shield is notoriously leaky against a massive, coordinated first strike of a thousand warheads, but far more effective against a ragged, disorganized second strike launched by the handful of submarines that survived an initial surprise attack. Therefore, building a city shield looks to the adversary like preparation to launch a disarming first strike and then hide behind the shield to mop up the weakened retaliation.
- * Erosion of Retaliatory Credibility: Because the United States based its entire defense posture on a guaranteed assured destruction capability against Soviet industry and command centers, every Galosh interceptor battery erected around Moscow reduced the expected number of American warheads arriving on target, legally and strategically compelling the Pentagon to neutralize the shield.
- * The Asymmetric Cost-Exchange Ratio: Under the physics of re-entry vehicles, building radar arrays and nuclear-tipped interceptor missiles to shoot down warheads at twenty-five thousand miles per hour cost roughly four to ten times more than building additional offensive warheads, chaff clouds, and inflatable Mylar decoys to saturate the radar.
- * The MIRV Escalation Ratchet: Rather than waste tens of billions of dollars matching Moscow shield-for-shield, McNamara told Kosygin calmly that the United States would simply multiply its offensive payload—fitting every single Minuteman III and Poseidon missile with Multiple Independently Targetable Re-entry Vehicles (MIRVs) so one booster spat out three to ten separate thermonuclear warheads plus dozens of decoys, leaving both nations vastly poorer and exposed to ten times the megatonnage.
At a press conference two days later in New York, Kosygin still maintained publicly that defensive systems were meant to save human lives rather than kill them. Behind closed doors inside the Soviet Ministry of Defense and the Academy of Sciences, however, physicists including Andrei Sakharov and military analysts ran McNamara's MIRV saturation equations and reached the identical mathematical conclusion. Three months after Glassboro, on September 18, 1967, McNamara delivered his landmark speech to United Press International editors in San Francisco warning against the mad momentum of the action-reaction offensive-defensive cycle. Five years after Kosygin pounded the table at Glassboro defending the morality of missile shields, the United States and the Soviet Union signed the May 1972 ABM Treaty in Moscow—legally binding both mortal enemies to leave their populations completely undefended.