This year’s Winter Olympics are being held in Pyeongchang, a mountainous region of South Korea located just 50 miles away from North Korea. In a surprise move, North Korea and South Korea have united under one flag for the games. This is extremely unusual because the two countries—and their citizens—have been separated by one of the most heavily armed borders in the world since the 1950s.

North Korea is ruled by a volatile dictator, Kim Jong-un. The country is developing nuclear warheads which may now have the capability to reach the U.S. Rising tensions between the U.S. (a longtime ally of South Korea) and North Korea are particularly alarming given the verbal sparring that’s been going on between Jong-un and America’s own unstable leader, Donald Trump.

Jong-un surprised the world in his new year’s speech this year by saying he wanted to send a delegation to the Winter Olympics. This was a huge departure from the North’s position on the last Olympics hosted in South Korea in 1988. Not only did the North Korean government boycott the 1988 Olympics, but they also blew up a South Korean passenger plane ahead of the games, killing 115 passengers in an attempt to destabilize the South Korean government and scare off attendees.

Following Jong-un’s announcement, North Korea negotiated with South Korea and the International Olympic Committee, which culminated in the two countries marching under the “unified Korea” flag and organizing a unified women’s ice hockey team. North Koreans also came away from the negotiations with additional slots for their players, with 22 in their delegation, although just two had qualified on athletic merit.