TEL AVIV – There is a common threat that links the Sept. 11, 2012, Benghazi attack to both the Boston Marathon bombings and the terror assault on the In Amenas gas facility in southern Algeria in January. The thread runs through al-Qaida in the Arabian Peninsula, or AQAP, one of the most deadly members of the al-Qaida conglomerate. AQAP previously attempted several major attacks within the U.S. The group was the first al-Qaida member to comment on the Benghazi attack, releasing a statement arguing the assaults on the U.S. mission and nearby CIA annex were revenge for the death of...