HTS's ascent could see Iran step up cooperation with IS

This narrative is self-serving for Iran because it presents Iran and its allies as being firmly against IS and papers over Iran's own role in international terrorism, as evidenced by global terror acts conducted by the Iranian Revolutionary Guard Corps and Hezbollah. However, neither Iran and its proxies nor the Syrian regime of Bashar al-Assad were effective at securing Syria from IS attacks. It is documented that the number of IS attacks in Syria in 2024—when al-Assad was still in power and Hezbollah and other Iran-backed groups were active in Syria—was triple the number of such attacks in 2023. 

Transactional relations

Iran claimed success against IS in Iraq, where the Iran-backed militias of the Popular Mobilisation Forces (PMF) were hailed for their role in defeating IS militarily. However, some of the PMF factions had a transactional relationship with IS. Where such factions controlled parts of the Iraq-Syria border, some of them engaged in practices like hiring out roads between the two countries to IS affiliates, who, in return for paying the requested daily amount for hiring a road, would be granted the freedom to use the road to transport whatever they desired, including people, weapons, cash, oil, drugs, and other smuggled goods. Conversely, in the Badia area in Syria, Hezbollah used to pay IS in return for facilitating the passage of trucks transporting Captagon.

Iran and the Assad regime also used IS as a tool to weaken the Syrian opposition. In 2015, the Syrian army let IS advance to Palmyra to attack the Southern Front rebel faction, and in 2014 and 2018, the regime facilitated IS attacks on Sweida. In 2014, as IS advanced toward the city, the regime's intelligence provided the group with information that aided its occupation of the Sweida desert.

Simultaneously, the regime attempted to seize the heavy weaponry belonging to the Sheikhs of Dignity during the IS advance. In 2018, IS conducted coordinated suicide bombings and raids on Sweida that left more than 200 people dead. Pro-regime forces largely refrained from interfering with IS as it carried out its attack.

In northeastern Syria, IS-Iranian cooperation has been even more explicit. Last year, the Syrian Democratic Forces (SDF) arrested Mohammed Al-Bakheet, also known as Abu Ghamed, who used to be an IS fighter and later became the leader of the tribal factions in the city of Al-Mayadeen, who were supported by Iran and who were fighting the SDF. In 2021, IS, the IRGC and Hezbollah met in the Syrian Badia area, and since then, IS attacks have spared Iran-linked groups and concentrated on the SDF and the Global Coalition Against IS.

The close relationship between Iran-backed groups and IS in northeast Syria manifested itself vividly when the anti-Assad Syrian rebel offensive advanced towards the area in late 2024. Iran continues its funding of and communication with IS, while the Iran-backed groups that fled the north-east left their weapons and bases to IS, which has become a de facto Iranian tool threatening to destabilise Syria.

Such destabilisation would present the current HTS-led Syrian administration as weak, bolster Iran's narrative about its role in combatting insecurity, and create sectarian strife. On 11 January, Syrian authorities foiled an IS plot to attack the Sayeda Zeinab area in Damascus, the site of a major Shia shrine.

IS cooperation with Iran in this context is also partly driven by the group's desire for revenge against HTS. For years, IS and HTS engaged in a brutal rivalry. HTS was born out of the Islamist extremist groups that used to be part of or aligned with IS but later severed ties with IS and al-Qaida and began fighting them both ideologically and on the battlefield. The rise of HTS as the most dominant group in Syria post-Assad can feed the transactional cooperation between IS and Iran.

Possible scenarios

One scenario that could benefit this cooperation is if the SDF and Kurdish groups in Syria's northeast engage in escalated fighting with Turkish-backed groups. The risk here is that the SDF are in charge of the prisons and detention centres in the area holding thousands of IS fighters and members, who IS has persistently tried to free. If the SDF become distracted by fighting groups like the Turkish-backed Syrian National Army, then IS—with Iranian support—can take advantage of the opportunity and break into the prisons.

Another risk is due to the growing calls by the Iraqi government for those Iran-backed factions in Iraq which are acting outside the remit of the state to hand over their weapons and join the Iraqi army. Iran sees in this scenario the weakening of its influence in Iraq. With these groups having built their legitimacy on fighting IS, it is possible that Iran can activate IS cells to show that these groups' mission is not over.

A similar risk applies to Lebanon, where Hezbollah is grappling with increased domestic and international pressure to disarm. Since a ceasefire with Israel is in place, an IS attack becomes the only other excuse that Iran and Hezbollah can use to show that the Lebanese Armed Forces are too weak to secure Lebanon without Hezbollah's help.

Although IS has sometimes attacked Iran, the group is transactional at its core, engaging in deals with multiple actors for survival. Iran is now the major actor that could use this IS transactionalism to its advantage.