Add another drop of tragedy to the story of America’s reluctant, no-boots-on-the-ground operation in Libya in 2011: Weapons that were never secured after Muammar Gaddafi’s ouster made their way to Boko Haram, the Islamist terrorist organization now holding hundreds of Nigerian girls. Last May, Boko Haram staged an attack in the town of Bama, killing 55 innocents and freeing 100 prisoners. That month Reuters ran a story by Tim Cocks headlined “Nigeria’s Islamists staging bolder, deadlier comeback.” It explained: The Bama attack showed their substantial firepower, including machine guns, large numbers of rocket propelled grenades (RPGs) and pick-up trucks mounted with...