Deep inside a mountain in Kilju County, North Korean scientists detonated a nuclear device, sending shockwaves throughout the world. The nation's reclusive leader, Kim Jong-il, had been threatening to join the nuclear club for years, and now the world was forced to take him seriously. The blast, equivalent to 0.5-1 kilotons of TNT, was detected by seismic sensors, leaving no doubt about Pyongyang's newfound capabilities. As news spread, international leaders scrambled to respond, condemning the test and calling for sanctions. For the first time, the Hermit Kingdom had demonstrated its ability to build and detonate a nuclear weapon, rewriting the rules of geopolitics in East Asia.