The hundreds of South Korean and American warplanes simulating attacks during drills are most likely what led North Korea to test a record number of missiles this week, experts say, but Pyongyang may also be turning up the heat before a nuclear test. Analysts say North Korean leader Kim Jong Un seems to genuinely dislike the allied drills, and particularly the involvement of U.S. stealth fighters. "North Korea really does not like these large combined air exercises, especially since they employ F-35s that can be used for decapitation strikes against the regime and are very difficult for North Korean air defences to pick up," said Mason Richey, a professor at Hankuk University of Foreign Studies in Seoul.