Isis fighters have managed to make their own thermal batteries for surface-to-air missiles and remote-controlled car bombs, according to a new report.
The batteries have been manufactured in a "university of jihad" in the de facto capital of Isis (Islamic State), Raqqa, according to videos shown to Sky News.
Their development would be highly significant. While the group has captured large quantities of old missiles, few have been put to use as their batteries had decayed.
Isis have been pushed back in recent months in both Syria and Iraq thanks to their inability to strike back at air attacks from the Western allies, and now from Russian jets.
Coalition jets could now theoretically be at risk, though the most modern Western fighters are probably beyond the threat posed by older surface-to-air missiles of the sort owned by the Syrian Army, which Isis would have taken.