North Korea: Why War Is the Only Option Now
I calculate the deaths a successful detonation will cause by using the NukeMapwebsite. Since not every weapon can detonate in the same place, I set a weapon's impact equal to the average of a detonation over a range of cities. A weapon that detonates in Japan will cause deaths equal to the average of an air detonation over Tokyo and Kyoto. A weapon that detonates in South Korea will cause deaths equal to the average of an air detonation over Seoul and Busan. A weapon that detonates in the U.S. will cause deaths equal to the average of an air detonation over Los Angeles, San Francisco, Chicago, Washington D.C., and New York. I weigh South Korean, Japanese, and American lives equally. So, a successful detonation of a 20 kt weapon causes expected deaths of 112 thousand and the successful detonation of a 250 kt weapon causes expected deaths of 546 thousand.
Given these assumptions, a war in 2018 will cause 1.4 million Japanese-South Korean-U.S. deaths (25 weapons (20 kt) * 50% chance of successful detonation * 112,000 deaths per successful detonation). The number of deaths resulting from war will increase by 1.1 million per year (4 additional weapons (250 kt) * 50% chance of a successful detonation * 546 deaths per successful detonation). It follows that a war in 2019 will cause expected deaths of 2.5 million, a war in 2020 will cause expected deaths of 3.6 million, and so on. A war in 2048 will cause expected deaths of 34.2 million.
The Risk of Accidental Nuclear War
While both the Americans and the Soviets were rational actors during the Cold War (at least as rational as Kim Jong Un, anyway) and while both the Americans and the Soviets knew that nuclear war would have disastrous consequences, there were nonetheless a number of occasions when the Americans and the Soviets came very close to starting a nuclear war by accident. These near misses arose from a combination of military misunderstandings, technical malfunctions in early warning systems, and human error. To illustrate:
Military Misunderstandings: During the Cuban Missile Crisis, the Soviets sent a squadron of 4 submarines armed with nuclear torpedoes towards Cuba with the intention of establishing a base on the island (Operation Anadyr). The subs ran into the U.S. naval blockade. In the tense circumstances of the Crisis and under an enormous amount of stress, the captain of one of the subs came under the mistaken impression that his sub was under attack by a U.S. task force led by the carrier USS Randolph and that war may have already broken out. Thinking that they were doomed, the captain cried out "We will die, but we will sink them all..." using the nuclear torpedo. It is highly likely that a Soviet attack that destroyed a U.S. carrier with a nuclear weapon at the height of the Cuban Missile Crisis would have led to a full-scale war between the U.S. and the Soviet Union, and that this war, in turn, would have led to a nuclear exchange. Fortunately, the squadron chief of staff was also on board, and he was able to dissuade the captain from pursuing that course of action.
Reflecting upon the Crisis, Graham Allison wrote that while President Kennedy thought that the chance of nuclear war was between 33% and 50%, "what we have learned in later decades has done nothing to lengthen those odds."
Technical Malfunctions: In 1983–a time of high U.S.-Soviet tension–the Soviet Union's early warning system detected a signal that the U.S. had launched a first strike. The system indicated that the signal was of the highest possible level of reliability. In this situation, it was the duty officer's responsibility to report the alert and its reliability level to his superiors. Soviet nuclear protocols then required that the Soviets launch a counter-strike before the U.S. missiles hit. Fortunately, the duty officer on the night was Stanislav Petrov. He had a skeptical streak due to his scientific background, and he thought that the attack signal might be too reliable to be real. Torn between reporting and not reporting the alarm, he finally decided to disobey his explicit orders and to instead notify higher command that the system had malfunctioned. He believed that if any of his colleagues (all of whom had a military education) had been on duty that night, they would have reported the alarm as an attack. If the alarm had been passed on, it is possible and perhaps even likely that the Soviets would have followed protocols and launched an accidental first strike at the U.S.
Human Error: In 1979 a training tape simulating a full Soviet nuclear attack was somehow loaded onto the main NORAD early warning system. Fortunately (again), the flight time of Soviet missiles gave NORAD time to check the raw radar data to see if it confirmed the information on the early warning system before the U.S. had to take a launch-no launch decision. Finding that it did not, the U.S. did not launch a retaliatory strike by accident.