North Korea’s military conducted mortar drills ahead of the South and U.S. kicking off a large joint military exercise.

South Korea’s birth rate has dropped throughout much of the past decade, spelling trouble for the military as regional threats and global conflicts simmer.

South Korean President Lee Jae Myung vowed on Friday to “respect” North Korea’s political system and build “military trust,” a day after Pyongyang said it had no interest in improving relations with Seoul.