On May 15, 1975, U.S. Marines stormed a Cambodian island to rescue the crew of the seized merchant ship SS Mayaguez, not knowing the hostages had already been freed. More Americans died in the rescue than were rescued. Three Marines were left behind on the beach and later executed. And Gerald Ford's approval ratings went up. The Mayaguez Incident is the last battle of the Vietnam War, and it forces one of the hardest questions in American history: when a government uses military force to send a political message, what is that message worth?