powerful nuclear test yet in north korea. u.s. intelligence officials now say they are confident in north korea s claim that they detonated a hydrogen bomb more devastating than the atomic bombs dropped during world war ii. the concern now, that it could be mounted onto an intercontinental ballistic missile. tonight, the u.s. ambassador to the u.n. saying that north korea is, quote, begging for war. abc s chief foreign correspondent, terry moran, is in seoul, south kariorea tonigh. reporter: today in south korea, a show of force. f-15 fighter jets practicing bomb drops, missiles launched, live-fire maneuvers simulating an attack. this country s swift and angry response to north korea s startling nuclear test, its sixth and most alarming blast yet. north korean state tv celebrated the, quote, perfect success, and there were cheers on the streets of pyongyang. the explosion was so powerful it triggered a major earthquake, magnitude 6.3 with tremors felt across the region. and tonight,