The video opens with high-definition footage shot from a drone flying over an oil refinery in central Iraq, but this video isn’t from a multi-million-dollar American drone. It’s from a drone operated by the Islamic State that likely cost a few thousand dollars. And the refinery – Iraq’s largest – is held by government forces, who have been besieged by the militants for the better part of a year.

The video, called “Defiant Attack on the Apostates at the Refinery,” began appearing on jihadist-linked websites and Twitter accounts last week. It heralded an Islamic State assault on the oil refinery at Baiji, where Iraqi government soldiers have held out since last summer against surrounding Islamic State troops. In the end, the government kept hold of the refinery, the country’s largest, with the help of 47 airstrikes by the United States and a massive influx of Iraqi reinforcements.

But beyond the outcome of the refinery battle, military analysts who’ve viewed the video find it alarming because it shows that the Islamic State retains a surprisingly high level of military skill despite months of daily airstrikes by U.S. aircraft and their coalition allies. […]