Rare photos show life inside North Korea's top-secret military

• North 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 training.

Little is known about life inside the "hermit kingdom" of North Korea. Even less is known about the country's military — the fourth-largest in the world behind China, India, and the United States, according to World Population Review.