Participating U.S. forces included the Arleigh-Burke-class guided-missile destroyer USS William P. Lawrence and a maritime patrol aircraft, according to South Korean naval officials. South Korea contributed roughly 10 aircraft and 10 warships, including the destroyer ROKS Yulgok Yi I.

North Korean leader Kim Jong Un oversaw the country's air force drills and stressed the importance of a step-up in war preparation, according to state media.

The top military officers of South Korea and the US vowed to further strengthen the allies' trilateral security cooperation with Japan during their first video talks earlier this week, the

North Korea is in its "strongest strategic position in decades," the U.S. Defense Intelligence Agency said in a new assessment.