When announcing in 2002 that the U.S. would detain al Qaeda fighters at Guantanamo Bay, Cuba, then-Defense Secretary Donald Rumsfeld famously described the base as "the best, least worst place." Mr. Rumsfeld's quip distilled a truth: The U.S. would capture enemy fighters and leaders, and their detention, while messy, was of great military value.

For two years, President Barack Obama has pretended that terrorism is a crime, that prisoners are unwanted, and that Gitmo is unneeded. As a presidential candidate, he declared: "It's...