Nuclear weapons brought big changes in deterrent strategy because even a few nukes could devastate a country. Both the U.S. and USSR sought to insure against a nuclear attack by developing the ability to respond even after a surprise attack (a second strike capability). In other words, even if the USSR successfully attacked the U.S., the USSR would still be destroyed by a U.S. counterattack and vice versa. The name for this strategy was MAD, or Mutually Assured Destruction. Some analysts believe that in the early phases of the Cold War, the American numerical superiority in nuclear weapons gave it a big advantage over the USSR (so-called compellence). Then-Secretary of State John Foster Dulles liked to talk about “brinksmanship.”
However, both sides knew they were never actually going to attack because even if one side’s nukes killed more people than the other’s, the casualties on both sides would still be numbered in the millions. It was no comfort that Herman Kahn’s On Thermonuclear War claimed the U.S. would ‘win’ a nuclear war because it would ‘only’ lose 30 million dead, while the USSR would lose 50 million dead. Hundreds of books and studies were written during the Cold War on nuclear strategy, counter-strategy, counter-counter strategy, etc., justifying each side accumulating thousands of nukes. This arms race was another example of the security dilemma - building up your own forces causes the other side to feel insecure and build up their own forces, in an endless spiraling arms race.
Having even a few nukes totally changes the equation. For instance, China reportedly has about 260 warheads, versus about 5,000 controlled by the U.S. However, this is enough to ensure deterrence, because the U.S. would not do anything that would result in the destruction of U.S. cities and millions of deaths. This deterrent effect is why nation states struggle so desperately to obtain nuclear weapons.
During the Cold War, each side sincerely believed that the other wished to attack, so for 40 years both sides were on a hair trigger. The 1962 Cuban Missile Crisis was a close call, with both sides fingering the red button. At one point, a U.S. Navy destroyer was disobeying orders and going after a Russian submarine near Cuba. The Russian sub captain wanted to respond with a nuclear missile, which would have set off a full-scale nuclear war. Luckily, there was an admiral aboard who overruled him.
There were other close calls. On the U.S. side, on the first night a new computer system was introduced at NORAD Headquarters, it indicated a massive attack. Fortunately, cooler heads prevailed and it was eventually determined that the new system was so sensitive that it had mistaken the rising moon as an attack. On another occasion, a flock of migrating birds set off alarms. On the Russian side, at one point they sincerely believed the U.S. was going to follow a Russian tactic of attacking under the cover of war games, so the U.S. had to scale them down. On another occasion, a rogue Russian operator told Russian ships that war was underway with the U.S. Fortunately, they had the good sense to check, and a crisis was averted.
In 1995, the U.S. notified Russia of an upcoming test missile firing. Unfortunately, the information was not passed up the ladder. When the missile was fired, the Russians thought it carried an electromagnetic pulse weapon designed to fry all their defenses as a prelude to a full nuclear attack. They actually unpacked the nuclear ‘football’ with their nuclear launch codes. Fortunately, Russian President Boris Yeltsin insisted on checking with the Americans first, and Armageddon was avoided.
Both sides developed a strategic triad of land-based missiles, long-range bombers and nuclear submarines, so that even if some were destroyed in a Pearl Harbor-type sneak attack, the others could counter-attack. It is hard to believe today, but the U.S. Strategic Air Command kept hundreds of planes in the air 24/7 for over 40 years, so that even if their bases were attacked, the already-airborne bombers could carry out their missions.
Both sides built up the number of nuclear warheads until each side had about 15,000, enough to destroy the world several times over. Both sides also had extensive but largely useless civil defense programs with air raid drills and fallout shelters. During junior high school, we had a drill which required us to sit in the school hallways. Your author got in trouble by saying, “They want the bodies lined up neatly.”