Thursday’s test did not appear to demonstrate the weapon's full capacity, and it remains unclear how far North Korea has come in mastering technologies to ensure the warhead would withstand atmospheric reentry and accurately strike targets. Still, analysts said the test was likely a meaningful advance in North Korea's goal to build a nuclear arsenal that could directly threaten the United States. Later Friday, the U.S. flew nuclear-capable B-52 bombers to the Korean Peninsula for joint aerial training with South Korean warplanes in their latest show of force against North Korea.