In the narrow passage where a third of the world's oil moves by sea, Iran's Revolutionary Guards this week claimed a quiet but pointed prize: a U.S. unmanned submarine, the Dive-LD, built to see without being seen in the depths of contested waters. The Pentagon acknowledged the loss while minimizing its meaning, and the manufacturer called it an acceptable cost of doing business in dangerous places. Yet the incident speaks to something larger — the growing reliance on autonomous machines to wage the patient, invisible work of modern military competition, and the new kinds of vulnerability that