South Korea, the U.S. and Japan held a joint aerial exercise involving a U.S. B-1B strategic bomber on Wednesday in the wake of North Korea’s missile launches earlier in the week.

The Joint Chiefs of Staff(JCS) said the combined drill was held over an overlapping section of South Korea and Japan’s air defense identification zones east of Jeju Island.

Wednesday marked the 13th time this year a U.S. strategic bomber has been deployed to the Korean Peninsula and the second time this year the three allies held a joint aerial exercise.

The latest drill saw the participation of South Korean F-15K fighter jets, the U.S.’ F-16 Fighting Falcon jets and Japan’s F-2 support fighter aircraft.

The JCS said the exercise was arranged to implement defense-related accords discussed at the Camp David summit in April, to boost the allies’ response to the North’s threats involving nuclear weapons and missiles, and to demonstrate the three nations’ strong intent to jointly respond to such threats.