It’s one of those stories that sounds too far-fetched to be true — that a bear outside the fence at the Duluth Air Force Base nearly triggered World War III and a possible nuclear holocaust.

But in recent years more accounts of the incident have surfaced that the legend appears to be true. Or at least much of it.

In October 1962, at the height of the Cold War between the U.S. and Soviet Union, American spy planes spotted Soviet nuclear missiles being installed in Cuba. Tensions mounted as both sides inched closer to war. On Oct. 22, all U.S. armed forces were placed on DEFCON 3, halfway to actual war, with President John F. Kennedy under pressure from his military commanders to strike first. The Cuban Missile Crisis had begun.

Here’s where the Duluth bear comes in:

On the night of Oct. 25, a sentry walking guard duty at what was then the Duluth Air Force Base (it has since been converted to an Air National Guard base) apparently spotted a shadowy figure climbing the fence.

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Retired Adjutant Gen. Ray Klosowski of Duluth, an Air National Guard pilot who went on to command the 148th Fighter Squadron based at Duluth and later the entire Minnesota Air National Guard, said the incident at the Duluth air base happened about a year and a half before he arrived. But he said it was still being talked about for years after he joined the base in 1964.

“It was at the height of the Cold War, the Cuban Missile Crisis, and there were probably 130 nuclear weapons on the base in Duluth at that time … so they took security very seriously,’’ Klosowski said.

Here’s where the details get sketchy, but reports say the sentry — apparently assuming it was an intruder, maybe a Soviet saboteur — shot at the intruder and immediately set off the sabotage alarm. The same alarm was connected to multiple alarm systems at bases in neighboring states.

In this undated U.S. Air Force photo, a crew readies a Genie air-to-air missile with a nuclear warhead for mounting on an F-106. The same planes carrying the same missiles were nearly scrambled in October 1962 from a Wisconsin airfield after a black bear caused a disturbance at the Duluth Air Force Base. (Photo courtesy of U.S. Air Force)
In this undated U.S. Air Force photo, a crew readies a Genie air-to-air missile with a nuclear warhead for mounting on an F-106. The same planes carrying the same missiles were nearly scrambled in October 1962 from a Wisconsin airfield after a black bear caused a disturbance at the Duluth Air Force Base. (Photo courtesy of U.S. Air Force)

Again, details remain unclear, but apparently the intruder turned out to be a black bear, which ran back into the woods unscathed.

The sentry apparently reported the misidentification in time so none of the aircraft at the Duluth base scrambled on alert. In Duluth, the situation had been diffused. But at Volk Field Air National Guard Base near Tomah, Wisconsin, something went wrong.

Somehow, instead of setting off the alarm that would let the base know intruders were present at another base, the Volk Field alarm went off that triggered a “scramble’’ alert to the pilots: Take off as fast as you can and prepare for imminent combat.

As part of the DEFCON protocol, 161 of the Air Force’s F-106A Delta Dart interceptors had been moved from big air bases across the U.S. to several smaller bases, like Volk Field, to avoid Soviet detection. Volk was so small that it didn’t even have a control tower. Its missions were directed from the Duluth base.

The F-106s were intended to find and destroy Soviet bombers approaching the U.S. by firing a nuclear-tipped Genie air-to-air missile that could knock out an entire squadron of bombers, Klosowski noted. The alarm that was sounding told those Volk Field pilots that Soviet bombers were on their way to drop their nuclear bombs on the U.S. As far as they knew, World War III was about to begin.

“They were literally sitting, ready to go, on the field, at the ready … that’s how high the tensions were for war. And you would never take off with nuclear weapons on board unless there was an imminent threat to the country,’’ Klosowski said.

But, according to several versions of the story, an officer at Volk Field decided to call the Duluth base to get confirmation that it was indeed a scramble situation. He was told it was a false alarm. At that point, the officer drove a Jeep out onto the runway, lights flashing, to stop the planes from taking off. (It’s not clear why he didn’t have a radio.)

As legend has it, that last-minute phone call may have prevented a black bear in Duluth from starting World War III and possible global nuclear annihilation.

Of course, it’s not certain or even likely the Volk Field planes would have gone very far north without being told the incident was a false alarm. But in those hectic days, nothing could be for sure. It’s also possible that, with many U.S. bombers in the air constantly at the time to avoid being destroyed on the ground, the U.S. interceptors might have fired their nuclear missiles at the wrong targets.

Later it was determined that, in the haste to wire new alarms at Volk Field as the Cuban Missile Crisis was unfolding, the installer had crossed wires, mixing the intruder alarm with the scramble alarm.

Much of the Duluth bear story remained classified and mostly under wraps for decades. It came out in declassified Air Force documents and was first reported by Stanford University professor Scott Sagan in his 1993 book, "The Limits of Safety: Organizations, Accidents, and Nuclear Weapons." The incident is one of many Sagan reports in the book — fires, crashes, mishaps, miscommunications — when U.S. nuclear weapons may well have gone off if circumstances had changed ever so slightly.

"The Limits of Safety: Organizations, Accidents, and Nuclear Weapons" by Scott Sagan.
"The Limits of Safety: Organizations, Accidents, and Nuclear Weapons" by Scott Sagan.

Sagan interviewed Dan Barry, an Air Force pilot who was 27 back in 1962. He remembered scrambling at Volk Field, ready to take off into war. Barry remembers his plane being second in line to take off when he saw a truck speeding toward them, lights flashing, he told the La Crosse Tribune in a 2009 interview.

Barry, who in 2009 was living in Seattle, retired from the Air Force in 1986 as a colonel. After they were told to stand down, the pilots assumed something had shorted out the alarm system. Later, they heard rumor that it was a drunk airman trying to sneak back onto the Duluth base.

It wasn't until Sagan called him that Barry learned it was a bear that started it all. As Sagan wrote in his book, the incident would almost be comical if it weren't part of a pattern of near-misses over the years that could have led to nuclear war.

"That was serious business," Barry told the La Crosse Tribune in 2009. "We'd never flown with a nuke on board. … It was really serious. I can remember almost expecting to see inbound nuclear missiles."

For his part, Klosowski said the bear intruder and subsequent false alarm probably weren’t as close to causing a nuclear disaster as others assume.

“They would have been in contact with their command center. … They would have had to clear it with the Canadians. … There were other measures in place to prevent them from firing their weapons before they knew exactly what they were doing,’’ Klosowski said. “But I can imagine it was still nerve-wracking at the time.”