On 9/11 the U.S. had effectively no counterterrorism doctrine. Fast forward ten years: Osama bin Laden is dead; al Qaeda is organizationally ruined and pinned in the tribal areas of Pakistan and Afghanistan; there has been no major attack on American soil; and while there has been at least one instance of a massive planned attack, it was crushed by the greatest international collaboration of intelligence services seen since the end of the Cold War. It's been a remarkable transformation.

Aki Peritz and Eric Rosenbach have experienced first-hand the monumental strategy changes in our...