Turkish president Recep Tayyip Erdoğan said in an interview with America’s PBS earlier this week he still considers his Syrian counterpart, Bashar al-Assad, as much a threat to the Middle East as the militant group that calls itself the Islamic State. It was Assad who “left space” for terrorist organizations like it, he said. “He was the one who prepared the ground for this.”

Surely, Erdoğan’s resentment has something to do with his failure to rein in Assad despite cultivating a close personal relationship with him in the years preceding the Syrian conflict. When Assad refused to heed Erdoğan’s calls for political reform, Turkey went on to support the largely Sunni uprising against the Syrian dictator.

But that doesn’t mean Erdoğan is wrong. There are, in fact, many indications Assad not only “left space” for the Islamic State, and radical Islamist groups like it, but that his regime actively helped it rise to prominence.

That is what a former Alawite member of Syria’s Military Intelligence Directorate, one of the country’s myriad intelligence services, told Abu Dhabi’s The National newspaper earlier this year. While many political prisoners and protesters involved in peaceful demonstrations against Assad’s government were kept in prison, fanatics and violent offenders were quietly released in late 2011, he said. “The regime did not just open the door to the prisons and let these extremists out, it facilitated them in their work, in their creation of armed brigades.”

Britain’s The Telegraph also reported that the regime “deliberately released militant prisoners to strengthen jihadist ranks at the expense of moderate rebel forces. The aim was to persuade the West that the uprising was sponsored by Islamist militants including Al Qaeda as a way of stopping Western support for it.”

John Kerry, America’s secretary of state, recognized as much earlier this year when he said of Assad’s clandestine support for terrorist organizations, “He’s been doing this for months, trying to make himself the protector of Syria against extremists.”

This was part of a larger effort on Assad’s part to radicalize the opposition against his regime. The Atlantic Sentinel‘s Daniel DePetris reported two years ago that forces loyal to Assad, including Alawite militias, were perpetrating massacres against Sunni Arabs to drive the conflict “into just the type of sectarian onslaught that ruined [Iraq] five years earlier.”

Syria’s security establishment knew exactly how to bring about such an outcome for it played an integral part in the Iraqi civil war. It was Syrian intelligence that facilitated the movement of foreign jihadists into Iraq throughout 2006 and 2007. It maintained close contact with Islamist agitators and militants at the time and there is little reason to suspect those ties were cut.

It seems Syria’s spies copied this policy in their own country. A defector from the group that then called itself the Islamic State in Iraq and Syria (ISIS) said, “They grew long beards and joined. When I asked my emir, I was told they had defected from the regime. But this does not make sense because ISIS doesn’t accept defectors. They killed a friend of mine because they discovered he had been in the military as a normal soldier.”

The Syrian National Council, a coalition of opposition groups based in Istanbul, made similar claims in February, saying several ISIS commanders were in fact former intelligence or military operatives. The group also pointed out that the Syrian Air Force had yet to bomb any of the Islamist group’s camps or headquarters in the northeast of the country while rebels in the south were routinely attacked by helicopter gunships and fighter jets.

That hasn’t changed. The Syrian army hardly operates in the northeast, if at all. That might appear to make some military sense, given that Syria’s economy and population are concentrated in the west. Except its oilfields are in the east.

It turns out the Assad regime is colluding with the militants to ship oil from under the territory they control, providing them with money to buy weapons and build the institutions they need for their “Islamic State”.

The same Telegraph story cited earlier says Assad “financed” the jihadists “by selling oil and gas from wells under their control to and through the regime.” The Guardian similarly reported in May that in some areas, the terror group known as Jabhat al-Nusra, which is a branch of Al Qaeda, had “struck deals with government forces to allow the transfer of crude across the front lines to the Mediterranean coast.”

No wonder Erdoğan insisted that the situation in Iraq, where the Islamic State has made significant territorial gains in recent months, prompting military intervention from neighboring Arab countries and the United States this week, cannot be seen separately from the situation in Syria. A strategy to defeat the Islamic State, it seems, would be incomplete without a plan to remove Assad — or at least remove the support he provides to it.