Unlike nationalist and Muslim Brotherhood-aligned groups, it has never been firmly established that terrorist organizations like ISIS benefitted from direct state sponsorship. ISIS did, however, manage to get a hold of both private funding and significant quantities of foreign armaments, including U.S. arms, during the maelstrom of the wars in Syria and Iraq.The above is from The Intercept's October 24 article by Murtaza Hussain, NSA document says Saudi prince directly ordered coordinated attack by Syrian rebels on Damascus.
Mr Hussain is in error. The Islamic State's oil trade with Turkey was too large and too openly conducted to be the work of rogue elements in the Turkish regime or its military; it was a straight-up business transaction between the regime and the terrorist outfit. This of course constituted direct state sponsorship of Islamic State.
The sponsorship ended only when the Russian and Syrian air forces bombed it out of existence, with a red-faced American regime contributing a few bombing raids on IS oil tanker convoys for appearance's sake.
However, the illicit trade was conducted for many months right under the noses of U.S.-NATO satellites. So it could be fairly said that in addition to direct state sponsorship by NATO member Turkey, IS received indirect sponsorship from NATO itself.
As to the rest of Hussain's article -- he spends little time on Saudi predations in Syria. He and various sources he quotes muse a bit on the proxy warfare in Syria that they refuse to concede dominated the war there. But much of the article is simply his opportunity to fatuously summarize the war from the viewpoint of goons who were paid by a host of state regimes to destroy a society. Even the title of the Intercept article, which describes the attackers who targeted Damascus as "rebels," is a silly attempt at a whitewash, as this passage from the article underscores:
The U.S. [NSA] document, based on surveillance of “opposition plans and operations,” did not indicate whether the attacks deliberately targeted civilians or involved any extremist groups — but it did show that American spies found out about the attacks several days before they were launched.********