Are you watching, North Korea? The United States and South Korea began a series of war games Sunday morning, essentially as a display of military might to make a point to an increasingly belligerent North Korea. Nicknamed Invincible Spirit, the military exercise features some 8,000 military personnel, 20 ships and submarines, and 200 aircraft. One of the drills focuses on handling enemy submarines, specifically creating a situation similar to the one that led to the sinking of the Cheonan, possibly by a North Korean torpedo. "The anti-sub-infiltration exercise works like this: if a sub is coming in to attack a ship, the military finds it and prosecutes it," one Navy commander said. North Korea, needless to say, is not pleased by the military exercise. “The DPRK is prepared for both dialogue and war,” a North Korean foreign ministry spokesman said. “It will remain unfazed by military threat and sanctions."