The U.S. Defense Intelligence Agency says North Korean leader Kim Jong-un has consolidated his power by replacing older, high-ranking personnel in the regime and military with a younger generation of officials.This according to a report released by Defense Intelligence Agency Director Michael Flynn, in which he also says key posts have been assigned to people very close to the North Korean leader.The report also mentions the recent execution of Kim's uncle, Jang Song-thaek, emphasizing the move shows Kim is not willing to tolerate defiance in any form.Flynn and Director of National Intelligence James Clapper spoke about global threats to a Senate panel on Tuesday, with both saying North Korea is a threat to U.S. national security.