On August 29, 1949, the Soviet Union tested its first atomic bomb, years earlier than most American officials had expected. The American monopoly was over, and the arms race had begun. Within a decade both sides had hydrogen bombs hundreds of times more powerful than the weapon that destroyed Hiroshima, and by the mid 1980s the two superpowers held around 70,000 nuclear warheads between them.
The logic of deterrence
Nuclear weapons changed the meaning of military power. A country could win a war in the old sense only if it could survive it. Deterrence means preventing an attack by threatening retaliation the attacker cannot accept. As each side built long range bombers, then intercontinental ballistic missiles in the late 1950s, then missiles carried on submarines that were nearly impossible to find, the two reached a condition strategists called mutually assured destruction. Mutually assured destruction was the condition in which each side could destroy the other even after being struck first. The key ingredient was a secure second strike: weapons that would survive any surprise attack and could still retaliate.
The size of the weapons was hard to grasp. In October 1961 the Soviet Union exploded the largest bomb ever tested, often called the Tsar Bomba, with a yield of about 50 megatons, more than 3,000 times the Hiroshima bomb. Testing in the open air spread radioactive fallout around the world, and scientists found strontium 90 from the tests in children's teeth.
Defenders and critics
Defenders of deterrence argue that it worked. The great powers, which had fought two world wars in thirty years, did not fight each other directly for the rest of the century, and fear of nuclear war pushed leaders toward caution in every crisis. Critics answer that deterrence rested on a threat to kill millions of civilians, which many ethicists and religious leaders judged deeply wrong, and that it depended on luck as much as logic. False alarms, lost bombs and misread signals happened again and again. A system that must work perfectly forever, they argue, will eventually fail. The moral question of whether threatening innocent people can ever be justified is one Universal Humanism cannot ignore.
Cuba, October 1962
In April 1961 a force of Cuban exiles trained by the CIA landed at the Bay of Pigs, hoping to topple Fidel Castro's revolutionary government. It was crushed within days. Castro drew closer to Moscow, and in 1962 Nikita Khrushchev secretly began placing nuclear missiles in Cuba. His motives included defending Cuba from invasion and offsetting American superiority in long range missiles, as well as answering American missiles already based in Turkey, on the Soviet border.
On October 14, 1962, an American spy plane photographed missile sites under construction. President Kennedy's advisers debated an air strike and an invasion. Kennedy chose a naval quarantine of Cuba instead of an immediate air strike, giving Khrushchev time to back down. The most dangerous day was October 27, when an American spy plane was shot down over Cuba. On a Soviet submarine near the quarantine line, being forced to surface by American depth charges, the officer Vasili Arkhipov refused to agree to the launch of a nuclear torpedo. The next day the crisis ended. Khrushchev removed the missiles in return for a US pledge not to invade Cuba and a secret promise to remove US missiles from Turkey. Only decades later did Americans learn that Soviet forces in Cuba had also held short range nuclear weapons ready for use against an invasion.
Learning to manage the danger
The crisis frightened both leaders into new habits. In 1963 the two sides set up a direct hotline between Washington and Moscow so leaders could communicate quickly. The same year, the Limited Test Ban Treaty banned nuclear tests in the atmosphere, in space and underwater. The Nuclear Non-Proliferation Treaty of 1968 aimed to stop the spread of nuclear weapons to more countries, in return for a promise from the nuclear powers to work toward disarmament. The chemical weapons treaties covered in CHEM 101 grew from similar fears.
Worked example: a false alarm in 1983
Shortly after midnight on September 26, 1983, Lieutenant Colonel Stanislav Petrov was on duty at a Soviet early warning center near Moscow when the satellite system reported an American missile launch, then several more. Tension was high: weeks earlier, Soviet fighters had shot down a Korean airliner, killing all 269 people aboard. Petrov's job was to pass the warning up the chain, where leaders would have minutes to decide on retaliation. He reasoned that a real American first strike would involve hundreds of missiles, not five, and that the new system was untested. He reported a malfunction instead. He was right: sunlight reflecting off high clouds had fooled the satellites. Apply the debate above. Defenders can say the system had human checks, and one worked. Critics can say the fate of millions rested on one tired officer's hunch at midnight. Both are true, and that is the unsettling heart of nuclear deterrence.