Maysam Behravesh is a political analyst at Persis Media and PhD candidate at the department of political science at Sweden's Lund University. He was an intelligence analyst and policy advisor in Iran from 2008 to 2010.

On Sunday, Hay’et Tahrir al-Sham (HTS), a former al-Qaeda affiliate based in Syria’s Idlib, signalled that it might abide by the terms of a September 17 deal between Russia and Turkey to prevent a Syrian government offensive on the rebel-held province. However, only a day later, the group missed a deadline to remove its fighters from a planned buffer zone around the province set in the Russia – Turkey deal. “We have not abandoned our choice of jihad and fighting towards implementing our blessed revolution,” HTS said in a statement.

Syrian authorities were quick to express their dissatisfaction. In a news conference on Monday, Syrian Foreign Minister Walid al-Moallem said the national army was deployed near Idlib, ready to attack if the rebels didn’t withdraw. “After Idlib, our target is east of the Euphrates,” the minister added, referring to territory held by predominantly Kurdish Syrian Democratic Forces (SDF) backed by the US. His statement echoed earlier comments by Syrian President Bashar al-Assad that the Russia-Turkey agreement over Idlib was only “a temporary measure“, and that the province will eventually return to the Syrian state. Assad and Moallem’s comments signalling a military offensive on Idlib came despite assurances by Russia’s President Vladimir Putin that no further major military actions are planned in the region.

Its vocal objection to the presence of al-Qaeda affiliated fighters in Idlib notwithstanding, the Syrian government has a long history of using groups similar to HTS – whose predecessor, al-Nusra Front, was designated a terrorist organisation by the US, the UK, France, Russia, Turkey, Iran and the UN among others – strategically to undermine the opposition and seize territory. In fact, they used such groups, the Islamic State of Iraq and the Levant (ISIL, known as ISIS) chief among them, for political and military leverage quite frequently throughout Syria’s eight-year civil war.

Only a week after Putin and his Turkish counterpart Recep Tayyip Erdogan agreed to create a demilitarised buffer zone in Idlib to avert a looming government offensive, the Assad regime reportedly ferried hundreds of ISIL fighters overnight from the eastern province of Deir az Zor near the Iraqi border to the outskirts of Idlib in northwest Syria.

“Regime forces transported more than 400 ISIL fighters late Sunday from the desert near the town of Albu Kamal,” the Syrian Observatory for Human Rights, a Britain-based monitor, said. The controversial measure had two distinct purposes: clearing the area around Al-Bukamal, where Iran-backed militia forces have a strong presence, of ISIL fighters and, perhaps more importantly, build a stronger case for the recapture of Idlib.

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In May, the Assad regime transported as many as 1,600 ISIL fighters and family members from the Hajar al-Aswad district and Palestinian Yarmouk refugee camp – an ISIL stronghold in southern Damascus since April 2015 – to the Badiya region, a vast stretch of desert in southeast Syria. The transfer paved the way for the government to retake full control of the capital after many years.

The government’s chief allies, Iran and Lebanese Hezbollah, have also supported such arrangements for military and political gains in the Syrian civil war.

Perhaps the most controversial of all was an Iran-blessed deal between Hezbollah and ISIL in August 2017 which saw hundreds of ISIL fighters and their families leaving, under Syrian military escort, an enclave on the border with Lebanon for the eastern province of Deir az Zor. According to the Hezbollah leader Seyed Hassan Nasrallah, the Iran-backed group accepted an unprecedented arrangement with a “terrorist” foe – which drew rare criticism from the Iraqi government among others – to find out the fate of nine Lebanese soldiers in ISIL captivity since 2014.

The deal, however, served a bigger objective, purging the Syrian-Lebanese border regions of ISIL presence and handing a much-needed political victory to Hezbollah whose reputation had suffered at home for sacrificing Lebanese interests to fight Bashar al-Assad’s civil war. It was also meant to reinforce ISIL ranks in eastern Syria in their fight against US-backed Kurdish forces and thus pit two nemeses of the Syrian government against each other. Rather unsurprisingly, the US warplanes struck parts of the convoy, blocking its progress to Al-Bukamal in Deir az Zor – reportedly the fighters’ final destination – and forcing it to redirect towards lightly populated areas in the Homs province, central Syria.

The strategic use of groups like ISIL and HTS was, of course, not limited to the Syrian government and its Iranian and Lebanese allies. Turkey and the United States, traditional backers of the opposition since the outbreak of the Syrian civil war, have also occasionally taken advantage of the presence of these groups in the country to obtain leverage against the Syrian regime.

Yet, it can’t be denied that the Assad regime was the actor that benefited the most from the emergence of groups like ISIL in Syria. Arguably their existence made Assad’s irreversible victory in the country’s 8-year civil war possible. One of the most effective strategies the Syrian government and its allies adopted to kill Syria’s popular revolution was to empower the extremist elements within the opposition. Syrian government’s calculated actions helped groups like ISIL and al-Qaeda to overshadow the legitimate opposition in Syria and set the stage for the creation of a toxic secularist-terrorist binary, where the Syrian Arab Republic under Assad was promoted to represent the former and ISIL and al-Qaeda stood for the latter. Over time, the practical and ideological lines between ISIL – al-Qaeda fighters and mostly nationalist rebels got blurry as the revolutionary opposition strived to stay relevant in an increasingly radicalised rebellion, enabling the Assad regime to lump them together as a “terrorist constellation” that needed to be uprooted altogether. Notably, the international community and particularly western powers, which were originally sympathetic to Syria’s Arab Spring, accepted the Syrian regime as the lesser evil and gradually abandoned the opposition.

Assad’s victory in the Syrian civil war would have been much more difficult absent the likes of ISIL and al-Qaeda.

The views expressed in this article are the author’s own and do not necessarily reflect Al Jazeera’s editorial stance.