North Korea’s military has fired hundreds of artillery shells into waters off the nation’s west coast, in an action condemned by South Korea as a violation of an agreement not to engage in provocative actions near the two countries’ shared border. This follows a series of joint war games by the U.S., Japan and South Korea. On Wednesday, U.S. and South Korean forces practiced a joint river-crossing drill south of the capital of Seoul involving helicopter gunships, tanks, artillery and other heavy weaponry.