A North Korean woman and soldiers look at a Chinese tour boat from the banks of the Yalu River near the North Korean town of Sinuiju, opposite the Chinese border city of Dandong.REUTERS/Jason LeeNorth Korea's military, the fourth-largest in the world, remains shrouded in mystery.Both men and women are required to serve in the military in North Korea.Kim Jong Un, the supreme leader of North Korea, has no formal military experience.Little is known…