 Ever since the end of World War II, the planet has faced the threat of nuclear war. Doomsday scenarios have usually involved two countries, the U.S. and Russia, but they are not the only two nuclear powers. Increasingly, there is another player that demands consideration, China. This summer, we're examining the competitive tension between the U.S. and China with senior journalist Jane Perlez. Today, we examine China's intent for its nuclear weapons. Here's Jane.