A seagoing vessel or aircraft approaching a warship of the U.S. — or any nation, for that matter — must identify itself or face what could be lethal consequences. Conventional spycraft take time to reach their target and can be immobilized before breaching a ship’s security. But what about a drone, quickly zipping above and around a ship, gathering its spy data, and then just as quickly vanishing? Welcome to a new military headache. What’s more, a drone incursion may be more than a spy venture, but an attack. While U.S. and Japanese officials are somewhat vague about the origins of the video…