South Korean and U.S. forces are conducting a joint military drill to prepare for military operations in underground environments, such as North Korea’s tunnels. 

The South Korean Army’s Ground Operations Command said it launched the four-day drill Monday at a training ground in Paju, Gyeonggi Province, as part of the Freedom Shield joint military exercises. 

The drill involves the participation of some 370 troops from both countries, including troops from the Ground Operations Command’s Special Maneuver Supporting Brigade, the Capital Mechanized Infantry Division, the 30th Armored Brigade, the U.S. Army’s Second Infantry Division and the South Korea-U.S. Combined Division. 

The drill is focused on refining combat methods in the North’s underground tunnels, underground storage facilities for weapons of mass destruction, subways and utility tunnels.
 
The North is suspected of having thousands of underground bases and hideouts.