AP Photo

As two heavily armed terrorists barged through the front doors of the five-star Oberoi Trident hotel in the Indian city of Mumbai, their cell phone rang. “Are you there?” a voice asked. On learning that the men were, indeed, at the appointed place, the same voice said, in a tone so soothing it could have been that of a doctor coddling a terminal patient: “You’re very close to heaven, brother.”

A year ago, 10 young jihadist men—brainwashed to the core of what passed for their souls—set out from training camps in neighboring Pakistan in search of a murderous place in heaven, the path to which ran through Mumbai. Members of Lashkar-e-Taiba, or the Righteous Army, their goal—messianic and mesmerizing—was to sow as much havoc in a city of 15 million as it was...