U.S. and South Korean forces held joint training on countering North Korea’s extensive network of underground military installations on Monday, kicking off the second week of their large-scale Freedom Shield spring exercises.

Approximately 370 personnel from both nations are participating in the underground warfare drill set to run for four days, according to the ROK army, emphasizing that the DPRK is estimated to have thousands of subterranean facilities that serve as key military strongholds and command centers.

“This training provides valuable opportunities for ROK and U.S. soldiers to operate as one team and exchange combat techniques for underground operations,” said