The U.S. and South Korea conducted joint naval exercises in the Sea of Japan on Monday amid growing tensions with North Korea over its nuclear weapons program.
The operation comes after Pyongyang's fifth and most powerful atomic test earlier this month — its second of the year — and was intended to "send a strong message of unified resolve," the U.S. and South Korea said in a joint statement.
The drills appeared to be the first coordinated operation by the allies outside of routine exercises since the Sept. 9 nuclear test.