South Korea and the United States have conducted a combined naval exercise in waters off the southeastern coastal city of Pohang. 

According to the South Korean Navy on Wednesday, the allies began the nine-day joint exercise on April 5 to improve their joint mine warfare capabilities.

The exercise, which concluded Tuesday, involved ten warships and three helicopters from both sides, including the South’s Nampo MLS-II minelayer and the U.S. mine countermeasures ship the USS Warrior. 

According to the Navy, the participants underwent training in laying, detecting and removing mines, as well as in operating mine-removal equipment. 

Capt. Lee Taeg-seon, commander of the South Korean Navy’s Mine Squadron 52, said that continued training in practical mine warfare will bolster the allies’ capabilities to protect major ports and maritime transportation routes in a contingency.