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On Sept. 11, the day he was killed in what we now know was an assassination deliberately planned to coincide with the terrorist attacks 11 years earlier, Ambassador J. Christopher Stevens approved a cable to the State Department warning about the deteriorating security situation in the Libyan city of Benghazi. The dispatch noted that the leaders of two militias, some of whose members were tasked with protecting the American consulate, had threatened to quit, in protest of alleged American support for a prime ministerial candidate they did not like. Two things stand out about the cable, obtained exclusively by The Daily Beast’s Eli Lake. The first is that there is no mention of the 14-minute online video, “Innocence of Muslims,” which the administration — in...