China's rapid naval buildup is challenging US dominance at sea

Since World War II, the US has built up the world's most powerful navy. But in recent years, China has been playing a game of catch-up and it now boasts the world's largest military fleet. Oriana Skylar Mastro discusses the situation. She's been an adviser on China strategy at the Pentagon and spoke to the World's Host Marco Werman in her civilian capacity, as the director of the Indo-Pacific Policy Lab at Stanford University.