Close Calls in the Nuclear Age.

The Badger Detonation: a 23 kiloton nuclear explosion fired on April 18, 1953 at the Nevada Test Site, part of Operation Upshot-Knothole.

There’s a formula for fun: Arm two superpowers to the teeth with thousands of nuclear warheads. Make sure they’re deeply hostile and suspicious of each other. Now cut off diplomatic communication, stir in about 50 smaller countries with their own agenda on each side, and - voilà! – cold war in a jiffy!

1. Suez Crisis

On November 5, 1956, during the Suez crisis, the North America Aerospace Defense Command (NORAD) received warnings that seemed to indicate that a large-scale Soviet attack was under way: a Soviet fleet was moving from the Black Sea to a more aggressive posture in the Aegean, 100 Soviet MiGs were detected flying over Syria, a British bomber had just been shot down in Syria, and unidentified aircraft were in flight over Turkey, causing the Turkish air force to go on high alert.

All signs pointed to the ominous, except that, not long after, each of the four warnings was found to have a completely innocent explanation. The Soviet fleet was conducting routine exercises, the MiGs were part of a normal escort – whose size had been exaggerated – for the president of Syria, the British bomber had made an emergency landing after mechanical problems, and last, but not least, the unidentified planes over Turkey? Well, they turned out to be a large flock of swans.

2. SAC-NORAD Communication Failure

On November 24, 1961, all communication links between U.S. Strategic Air Command (SAC) and NORAD suddenly went dead, cutting off the SAC from three early warning radar stations in England, Greenland, and Alaska.

The communication breakdown made no sense, though. After all, a widespread, total failure of all communication circuits was considered impossible, because the network included so many redundant systems that it should have been failsafe.

The only alternative explanation was that a full-scale Soviet nuclear first strike had occurred. As a result, all SAC bases were put on alert, and B-52 bomber crews warmed up their engines and moved their planes onto runways, awaiting orders to counterattack the Soviet Union with nuclear weapons. Luckily, those orders were never given. It was discovered that the circuits were not in fact redundant because they all ran through one relay station in Colorado, where a single motor had overheated and caused the entire system to fail.

3. U2 Spy Plane Accidentally Violates Soviet Airspace

U2 spy planes were high-altitude aircraft that took pictures of the Soviet Union with extremely powerful long-distance telephoto lenses. During the Cuban Missile Crisis of 1962, U2 pilots were ordered not to fly within 100 miles of the Soviet Union to avoid antagonizing the Soviets.

However, on October 26, 1962, a U2 pilot flying over the North Pole made a series of navigational errors because the shifting lights of the aurora borealis prevented him from taking accurate readings with his sextant. As a result, he ended up flying over the Chukotski Peninsula in northern Siberia, causing the Soviets to order a number of MiG interceptors to shoot his plane down immediately.

Instead of letting him be shot down, however, the United States responded quickly by sending out F-102A fighters armed with nuclear missiles to escort the U2 back to American airspace and prevent the MiGs from following it. Unbelievably, the tactic worked. Even more amazing: the decision whether to use their nuclear missiles was left to the American pilots, and could have easily resulted in a nuclear conflict.

4. When Camping, Make Sure to Hide Your Food and Your Nuclear Weapons

On October 25, 1962, again during the Cuban Missile Crisis, a security guard at an air base in Duluth, Minnesota, saw a shadowy figure scaling one of the fences enclosing the base. He shot at the intruder and activated an intruder alarm, automatically setting off intruder alarms at neighboring bases.

However, at the Volk Field air base in Wisconsin, the Klaxon loudspeaker had been wired incorrectly, and instead sounded an alarm ordering F-106A interceptors armed with nuclear missiles to take off. The pilots assumed that a full-scale nuclear conflict with the Soviet Union had begun, and the planes were about to take off when a car from the air traffic control tower raced down the tarmac and signaled the planes to stop. The intruder in Duluth had finally been identified: it was a bear.

5. A Terrifying Crash

On January 21, 1968, fire broke out on a B-52 carrying a nuclear payload near Greenland, forcing the crew to bail out. The unmanned plane then crashed about seven miles from the early warning radar station in Greenland.

The damage done could have been remarkable. The plane exploded as did the explosives surrounding the radioactive core of the nuclear weapons (which require conventional explosives to detonate). Given the state of nuclear weapons technology at the time, this type of unintentional detonation of conventional first-stage explosives could have theoretically triggered the second-stage fission reaction, resulting in a nuclear explosion. Luckily for the world, it didn’t.

The resulting explosion would have not only severed regular communications between the early warning station and NORAD, it would have also triggered an emergency alarm based on radiation readings taken by sensors near the station. The only conclusion at NORAD headquarters, in this grisly hypothetical but very plausible scenario, would have been that the Soviets were launching a preemptive nuclear strike, and the United States would have responded in kind.

6. Comp Fear

On November 9, 1979, four command centers for the U.S. nuclear arsenal received data on their radar screens indicating that the Soviet Union had launched a full-scale nuclear first strike on the United States. Over the next six minutes, planes were launched and nuclear missiles initialized for an immediate retaliatory strike.

The president’s National Emergency Airborne Command Post – an armored jump jet with radiation shielding and advanced communications capabilities, meant to allow the president to remain in contact with the government and armed forces during a nuclear war – was also launched, although curiously without the president aboard. However, the alarm was canceled because no sensors or satellites detected an actual Soviet missile launch. The alarm had been caused by computer software used for training exercises depicting a nightmare scenario Soviet first strike.

Senator Charles Percy, who happened to be at NORAD headquarters during this event, said the reaction was one of overwhelming panic and terror. Justifiably so.

7. Comp Fear, Part 2

Electronic displays at NORAD, the SAC, and the Pentagon included prominent, highly visible numeric counters showing the number of enemy nuclear missiles detected. They normally displayed four zeros – “0000” – indicating that no nuclear missiles had been launched.

However, on June 3, 1980, at 2:25 in the morning, the counters started randomly substituting the number “2” for “0.” As a result, crews manning bombers carrying nuclear weapons were ordered to begin to warm up their engines, Minuteman missiles were initialized for launch, and airborne command posts were also launched.

It was determined that this first even was a false alarm, but three days later it happened a second time – causing the entire emergency response procedure to start rolling once again. The problem was eventually traced back to a single faulty computer chip combined with faulty wiring.