On November 29, 1987, two North Korean spies boarded a South Korean plane in Baghdad. The pair had used fake names and forged passports to pose as Japanese tourists. They’d also convinced security to let them keep the batteries in their carry-on “radio,” which they’d turned on to demonstrate to security that it was harmless.

Except it wasn’t. The working “radio” was also a battery-powered bomb.

The spies planted it in an overhead bin, then exited the plane at a layover in Abu Dhabi. Once Korean Air Flight 858 was back in the air, the bomb exploded and killed all 115 people on board, most of them from South Korea. The authorities tracked down the spies, who tried to commit suicide with cyanide cigarettes. One of them died; the other survived and was extradited to South Korea—the same country where the Olympics were set to begin in 10 months.

Even though the bombing occurred nearly a year before the Olympics, Sergey Radchenko, a professor of international relations at Cardiff University in Wales, says he has “no doubt” the attack “was an effort to sabotage the Games.” He explains that North Korea was interested in creating an “atmosphere of fear that would force the IOC to move the Games somewhere else,” or at least to discourage other countries, like its allies, from attending.

The CIA had been worried about the danger North Korea posed to the 1988 Summer Games in Seoul even before the Korean Air bombing. However, the attack sparked new concerns in the intelligence agency.

“[The North Korean capital of] P’yongyang’s public threats against the 1988 Seoul Summer Olympics and its sabotage of a South Korean airliner last November clearly point to North Korea as the greatest challenge to the security of the Games,” the CIA wrote on May 3, 1988, in a now declassified memo. “Seoul is taking extensive precautions to prevent violence and agent infiltrations, but international air links to South Korea remain vulnerable to sabotage or to serving as transportation for terrorists.”

Thirty years later, the possibility of a North Korean attack during the Olympics is still a concern. For the 2018 Winter Games in Pyeongchang, the country will deploy fourtimes as many security officers as there were during the much larger 2016 Summer Games in Rio de Janeiro, Brazil. In addition, the country will release interceptor drones to catch and capture any “rogue drones” that might be poking around.

North Korea’s attempts to disrupt the Olympics started in the mid-80s, after the International Olympic Committee (IOC) had already selected South Korea to host the 1988 Olympics. Out of nowhere, North Korea approached South Korea and the IOC with an unexpected proposal: Could it co-host the 1988 Olympics with South Korea, splitting the events 50-50 between the two countries?

It was a strange request, considering that no country had ever officially co-hosted the Olympics with another before. And it was stranger still that this was coming from North Korea, whose tight control on visitors seemed logistically incompatible with a multi-country event like the Olympics. “It is difficult for me to think that North Korea can open its borders to more than ten thousand journalists and to all the members of the Olympic family,” remarked Juan Antonio Samaranch, president of the IOC, at a 1986 meeting about the request.

But ironically, North Korea probably didn’t think co-hosting was possible either.

“The North Koreans did not have a realistic expectation of co-hosting the Games in 1988,” Radchenko says. “They joined these talks with South Korea just to show to their allies, the Chinese and the Soviets, that they were being reasonable.”

Worried that China and the U.S.S.R. wouldn’t attend the Olympics if South Korea didn’t appear open to a discussion, the country offered to let North Korea co-host the Olympics by staging a few events. The thinking was that “if the North Koreans decide to do something stupid, their allies will be there to hold them back,” Radchenko says.

South Korea suggested North Korea could host tournaments for sports like football, table tennis, and archery (for the 2018 Olympics, South Korea made a similar proposal). But the offer was a much smaller piece of the Olympics than North Korea had asked for. The country wanted to host several full sports; not just a few tournaments within a sport, as the IOC had proposed for football.

By the fall of 1987, it was clear there would be no deal. Yet for North Korea, the most disappointing part was that they still weren’t able to convince the Soviet Union and China to boycott the event. In early 1988, both countries announced that they would attend the Olympics.

For South Korea, the fact that so many countries were participating was a diplomatic victory. The nation had only just transitioned from a military dictatorship to a democracy in 1987, and was eager to use the Olympics to introduce itself to the world.

“This was a huge event for South Korea in so many different ways,” says Craig Greenham, an Olympic historian and professor of kinesiology at the University of Windsor in Ontario, Canada. “South Korea didn’t have a well-known, and in some ways well-regarded, profile. And this changed after 1988.”

The Games were also a source of national pride. One poignant moment involved gold-medalist Sohn Kee-chung, who had won the men’s marathon at the Berlin Olympics in 1936. Back then, Korea was under Japanese occupation, so Sohn and other Korean athletes had to compete on Japanese teams. But at a press conference after his victory, Sohn stated that he was Korean, and that Japan was occupying his country.

“Flash forward 52 years, and the man who carried the torch into the stadium was Sohn Kee-chung,” says David Wallechinsky, president of the International Society of Olympic Historians and author of The Complete Book of the Olympics. “I remember him entering the stadium jumping up and down, this man in his 70s, and it was so moving. People were in tears.”

After the Olympics, Socialist Bloc countries began to abandon North Korea by giving South Korea diplomatic recognition, which they had previously denied. In a recent Politico article, historian Sheila Miyoshi Jagerargues that “the North Korean regime we face today—isolated, belligerent, desperately pumping up its dangerous nuclear program as its only leverage on the world stage—was born, in part, in 1988. At the Olympics.”

Radchenko agrees, saying the 1988 Olympics were “a lost opportunity to engage North Korea,” which boycotted the Games with Cuba and a few other countries. “The South Koreans were so keen to host their Games and, in a way, to humiliate North Korea,” he says, “that what they ended up with was a very bitter, isolated North Korea.”

Even though the 2018 Olympics promise more cooperation between North and South Korea, including a combined women’s ice hockey team, most experts do not expect to see an easing of tensions between the two countries.

“If anybody thinks that a joint female hockey team can somehow erase decades and decades of bad feelings, I think they’re dreaming in technicolor,” says Greenham.

It seems that even Kim Hyon-hui, the surviving spy from the 1988 Korean Air flight bombing, feels the same way. In an interview leading up to the 2018 Olympics, the North Korean dissident told NBC News that she thinks the joint hockey team is “a publicity stunt for Kim Jong Un,” rather than a sign that positive relations will follow.

“North Korea is using the Olympics as a weapon,” she said. “It’s trying to escape the sanctions by holding hands with South Korea, trying to break free from international isolation.”