The sudden appearance of four crane barges where a submarine had been parked has prompted questions about the possibility of an accident. Satellite imagery shows unusual activity last month, including the sudden appearance of four crane barges, at a shipyard in China that builds submarines and other naval vessels, which might potentially be a sign of an accident of some kind. Tom Shugart, an adjunct senior fellow at the Center for a New American Security (CNAS) think tank and a retired U.S. Navy submarine warfare officer, was first to notice the goings-on at the Wuchang Shipyard. This yard, which is...