The U.S. military is planning to fly a pair of B-1 long-range bombers over South Korea Tuesday as a show of the U.S. commitment to defend that country and Japan against the threat of a North Korean nuclear attack.

Last week, North Korea conducted its second nuclear detonation of the year, which it said was a successful test of a powerful warhead, small enough to fit atop a ballistic missile and reach the U.S. and its allies in the region.