The U.S. and Republic of Korea navies (ROKN) joined forces on Monday to conduct combined maritime exercises in the East Sea to demonstrate their anti-submarine warfare (ASW) and precision strike capabilities two weeks after North Korea’s fifth nuclear test.

The combined maritime drills were undertaken outside of the routine exercise cycle “for the first time” in a show of force against the North’s recent and continuing provocations, the Republic of Korea (ROK) Fleet and Commander, U.S. Naval Forces Korea (CNFK) said in a press release.

The U.S. and the South hold joint military exercises such as Key Resolve, Foal Eagle,