PARIS — On May 15, 1985, kidnappers in Lebanon released six Polaroid photos of men they held captive, including two American priests, two French diplomats, the American bureau chief for the Associated Press, and the head of the CIA station in Beirut: William Buckley.

But there was another photograph as well, an 8x10 color glossy of a man whose face was badly bent and his jaw twisted “as if it had been shattered with a sledgehammer.” The nose was broken. He was pale and emaciated, and forensic specialists had to work for days before they were certain that this, too, was William Buckley.

A few weeks later, on June 3, 1985, we now know, Buckley died. As Fred Burton and Samuel M. Katz write in their new book, Beirut Rules: The Murder of a CIA Station Chief and Hezbollah’s War Against America, this “American war hero, the Green Beret, the CIA paramilitary officer, and the one man in Langley courageous enough to accept the assignment in Beirut” had succumbed “in a south Beirut dungeon alone, tortured, savaged, and neglected.”