South Korea, the United States and Japan held their first joint aerial exercise on Sunday near the Korean Peninsula.

According to Seoul’s defense ministry, the three nations staged the joint drill in the overlapping section of the Air Defense Identification Zones of South Korea and Japan, south of the peninsula.

Joint air drills have been held often between Seoul and Washington or between the U.S. and Japan in the skies over or near the peninsula, but not among all three nations.

Sunday’s trilateral training involved fighter jets from the three nations, including the nuclear-capable B-52H from the U.S., with jets escorting the strategic bomber in formation.

The B-52H was deployed to South Korea last week and landed at a local air base for the first time in line with the U.S. agreement to strengthen its extended deterrence against North Korea’s nuclear threat and to increase the presence of its strategic assets around the peninsula.

The ministry said the training was held in accordance with the three countries’ earlier defense agreement reached at the trilateral summit in August to expand their joint response capabilities against North Korea’s evolving nuclear and missile threats.