The Islamic State [IS] group and the Assad regime in Syria have been colluding with each other, says Sky News – who are examining the documents – anywhere from making "tactical withdrawal" deals on the battleground to trading oil and fertilisers.
It has consistently been argued that Assad played a crucial role in the rise of IS and other extremist groups like al-Qaeda-linked Nusra Front. But the new revelations confirm a much more direct role.
Most notably, the much-hyped regime victory in the ancient city of Palmyra against IS seems to have been at least partly the result of a prior arrangement with the extremist group that had been in control of the city.
But the cooperation has been going on for years, the documents handed to Sky News seem to show.
Similar arrangements were apparently agreed in places other than Palmyra, whereby IS militants would withdraw from certain areas before the Syrian army moved in to "recapture" them.
A document written shortly before the Syrian army recaptured the ancient city reads: "Withdraw all heavy artillery and anti-aircraft machine guns from in and around Palmyra to Raqqa province," in reference to the de-facto capital of the group in eastern Syria.
|Withdraw all heavy artillery and anti-aircraft machine guns from in and around Palmyra to Raqqa province
- Islamic State leaked letter
|Click to enlarge|
Another letter contains instructions for a commander to "transfer all equipment and weapons to the agreed evacuation point", and adds: "We have received intelligence that al Qasr and its surroundings will be bombed on 24th November, 2013".
The alleged IS defectors who spoke to Sky News claimed this was a withdrawal agreed with the Syrian regime.
A third letter examined by the British network apparently requests safe passage for a driver through IS checkpoints "until he reaches the border with the Syrian regime to exchange oil for fertiliser".
The IS defectors told Sky News this was a trade agreement between the two sides that has been going on for years.
One of the defectors told Stuart Ramsay, the network's chief correspondent, that IS was coordinating the movement of its fighters and leaving areas they previously controlled, in direct coordination with the Syrian army and even the Russian air force.
|It may take 20 years before we know exactly what is going on
- Dr Afzal Ashraf, Royal United Services Institute
Although the Syrian regime and IS may well be colluding for tactical reasons related to short-term gains and working against worse enemies for them both, they have indeed fought one another, with scores killed on both sides.
All this paints a multi-layered picture of the Syrian conflict. Terror experts quoted by Sky News said the documents show this is arguably the most complicated war they have ever tried to make sense of.
"This is a war of perception and narrative and everyone is trying to manipulate events," said Dr Afzal Ashraf from the think tank Royal United Services Institute.
"It may take 20 years before...we know exactly what is going on," he added. "Almost certainly there will be some sort of communication going on between mortal enemies, and that is for short term tactical gains and losses.
"Certainly if there is economic trading going on, which we know there is, there would be communication."
Sky News say the authenticity of the documents, obtained via a Free Syrian Army-affiliated group that operates a network to smuggle defectors away from IS, is impossible to verify, but that all previous leaks of material funnelled through this group "have proved to be genuine".
The documents include copies of handwritten orders allegedly sent from IS's Raqqa headquarters.