American military chiefs have been left dumbstruck by an undetected Chinese submarine popping up at the heart of a recent Pacific exercise and close to the vast USS Kitty Hawk. By the time it surfaced, the 160ft Song Class diesel-electric attack submarine had sailed within viable range for launching torpedoes or missiles at the carrier. The incident caused consternation in the US Navy, which had no idea China’s fast-growing submarine fleet had reached such a level of sophistication.