The U.S. military sent four of its most advanced stealth fighter jets to accompany two strategic bombers in a flight over the Korean Peninsula for bombing drills on Thursday in a “direct response” to North Korea’s unprecedented launch over Japan of a missile designed to carry nuclear weapons two days earlier.

The dispatch of four of the U.S. military's most high-tech fighter jets — and the two heavy bombers — was almost certain to raise hackles with nuclear-armed North Korea.

The two Guam-based B-1B bombers were joined by the four F-35B fighters stationed at U.S. Marine Corps Air Station Iwakuni in Yamaguchi Prefecture for a joint training drill over Kyushu airspace. The fighters and bombers later linked up with South Korean Air Force F-15Ks for a flight over the Korean Peninsula.