Iran’s intervention in the Syrian civil war allowed it to strengthen its foothold in the country. Iran sent numerous foreign militants to Syria, recruited Syrians into Iranian Revolutionary Guard Corps (IRGC)-aligned militias, and carved out pockets of de facto territorial control for those allied militias. In recent years, however, several Arab countries have increased their efforts to normalize relations with Syria, and it is looking more likely that Syria will eventually return to Arab regional diplomacy.  The question then becomes how Iran might seek to preserve the gains it made in Syria, given that some Arab countries could use strengthened ties with Syria to undermine and side-line their own rival–Iran.
The Iranian Intervention
From the outbreak of the Syrian civil war, the IRGC played a vital role in supporting Syrian President Bashar al-Assad’s regime. IRGC Quds Force leader Qassem Soleimani headed an IRGC advisory mission to Syria as early as 2011.  By 2012, the IRGC were facilitating the transfer of material support, training and advising Assad’s forces, and organizing the recruitment and establishment of pro-regime militias. This support was vital given the large number of defections that Assad’s forces faced early in the conflict. Subsequent years saw Iran support the entry of Hezbollah and similarly Iranian-aligned Iraqi militias into the conflict, while Soleimani played a leading role in coordinating the Syrian army, Hezbollah, and the various pro-regime militias. The IRGC even found itself directly involved in fighting Syrian rebels at times. 
Iranian support, further bolstered by the Russian military intervention in 2015, shifted the tide of the conflict in Assad’s favour. At present, despite significant portions of north-western and north-eastern Syria remaining out of Assad’s control, the more populated western belt of the country — the part containing the majority of Syria’s major urban hubs — is firmly under Assad’s thumb. Iran, for its part, has gained over 300 military stations in Syria and its proxies, including both foreign and domestic, remain concentrated in strategic locations across the country (Jusoor, December 27, 2021).
Deir ez-Zor and Iranian Access to the Mediterranean
Iran’s initial intervention had been defensive and aimed at keeping ally Bashar al-Assad in power. The overthrow of Assad would have threatened Iran’s key strategic interests, including access through Syria to the Mediterranean, which allows Iran to connect with its proxy Hezbollah in Lebanon. Iranian fears came true in 2013 with the rise of the Islamic State (IS), which took control of large swathes of eastern Syria. IS control included the province of Deir ez-Zor, which directly threatened Iran’s land route to Syria due to its position bordering Iraq.
Syrian forces bolstered by IRGC-backed militias took back control of Deir ez-Zor in 2017. The IRGC and its proxies remained in the province following the victory, with the former establishing the Imam Ali military base and the latter imposing de facto control over several small urban hubs along the western bank of the Euphrates, including the border town of al-Bukamal, while also securing roads connecting the province to Homs, Raqqa and beyond.  With the al-Qaim Iraq-Syria border crossing reopening in 2019 and Iranian proxies firmly entrenched on both sides of the border, Iran had secured one of its principal interests in Syria (al-Jazeera, September 30, 2019). Specifically, Iran achieved direct influence over one of Syria’s three main border crossings from Iraq, thereby strengthening the land bridge from Iran across Iraq and Syria and into Lebanon and allowing Iran to support its proxies, strengthen its influence, and threaten its rivals.
The Militias of Deir ez-Zor
One of the ways Iran seeks to control areas of Deir ez-Zor and influence Syria is through the network of militias it maintains in the country. The largest militia organization in Syria is the National Defence Forces (NDF). The NDF, created with Soleimani’s help in 2012, is an umbrella organization centralizing the multitude of pro-Assad paramilitaries. At its peak, the NDF contained up to 100,000 militants. Not all NDF militias are aligned to Iran, however, as the NDF’s demographics reflect the diversity of the Syrian population. Several NDF militias nevertheless received training from Hezbollah and the IRGC, and some militants travelled to Iran for training. 
In Deir ez-Zor, the militias on the ground showed their allegiance to Iran most clearly. Iran inundated the province with foreign Iranian-aligned militias while recruiting local Syrians to form newer militias. Notably, Deir ez-Zor hosted a militia presence from pre-existing pro-Iranian Hezbollah and Iraqi militias, such as Kata’ib Hezbollah and the Badr Brigades.  Iran also facilitated the creation of new militias, namely Fatemiyoun and Zaynabiyoun, consisting of Shia militants imported from Afghanistan and Pakistan (Salaam Times, January 29, 2019). Locally, aided by its co-opting of several Arab tribes in the province, Iran additionally created militias made up entirely of Syrian recruits from tribes in the province (al-Monitor, October 24, 2021). These militias include Jaysh al-Qura, founded in 2019, and the Hashemiyoun, founded in 2021. Recruitment to these militias has been dependent on conversion and adherence to Iran’s Wilayat al-Faqih legal school of Shiism (al-Mashareq, April 1, 2021).
The Shi’ization of Deir ez-Zor
In May 2011, residents of al-Bukamal in Deir ez-Zor, which is majority Sunni, burned pictures of the leader of Hezbollah Hassan Nasrallah and chanted anti-Iran slogans.  Just over a decade since then, Iranian cultural and humanitarian organizations have firmly entrenched their presence in the province, rebuilding damaged infrastructure and setting up schools in which Farsi and Iranian history are taught. Shia proselytizing activities have been facilitated by scholarships for students wishing to pursue religious studies in Iran, while tribal sheikhs are offered financial support to help spread Shia Islam. Iran’s proselytizing has multiplied to the point that two Shia shrines have been built in the province, including Ain Ali Spring and the Dome of Ali, enabling Shia pilgrimages and granting the region a new Shia identity.  Direct coercion has also been used, with reports of arrests of Sunni imams for refusing to perform the Shia version of the call to prayer. Hospitals in some towns have also refused to admit Syrian locals without prior approval from the IRGC or IRGC affiliated militias.
Alongside proselytizing, Iran also facilitates demographic change. Iranian businessmen and companies have bought housing in al-Bukamal and Mayadin, granting the accommodation to foreign Shia families migrating to the area. Although there are no reliable statistics in Deir ez-Zor, given the influx of foreign Shia militants and their families alongside the hundreds of locals who have joined IRGC affiliated militias, it is likely that Iran has had significant success in changing the demographics of the province. Thus, in one of the area’s most vital to Iranian interests in Syria, Iran has laid the groundwork for a local population favorable to long-term Iranian influence.
Syrian Normalization with Arab States
For Assad to push Syria into the post-conflict phase, he requires regional legitimacy of his rule and foreign investment. Normalization of ties with regional powers leading to a return to the Arab League would grant Assad the legitimacy and the investment opportunity he seeks. Jordan, Egypt, and Algeria have all shown recent signs of deepening diplomatic activity with Syria.  However, the biggest prize for Assad remains normalization with the wealthy Gulf States. Assad has already had some success in re-expanding ties with the UAE and Bahrain, attaining limited investment with the the UAE (al-Arabiya, November 11, 2021). Significant Gulf investment in Syria and normalization of ties with regional powerhouse Saudi Arabia are, however, likely conditional on Syria curbing Iran’s footprint in the country. Given the security risk that deepening Iranian influence in Iraq and Yemen has posed Gulf countries, the UAE and Saudi Arabia’s motivation to counter Iran in Syria has increased (al-Jazeera, February 4).
Toward the end of 2021, Syria showed it would be receptive to reducing Iranian influence in the country, at least on the surface. In November, only days after the visit of the UAE foreign minister to Damascus, Assad ordered the Iranian commander of the Quds Force in Syria to leave the country for breaching Syrian sovereignty (Iran International, November 27, 2021). However, Assad is likely to be cautious about significantly moving against Iran over the coming years. After all Assad, who values staying in power above all other considerations, knows that Iran’s intervention kept his regime intact. Since multiple rebel groups remain active, pushing out Iran’s military and proxy militias would leave his regime vulnerable.
Iran, Syria, and the Arab World
It could be Iran that is most receptive to Syrian normalization with the Arab world. Iran could benefit politically, economically, and militarily from normalization, including by reducing its direct military presence. If Iran believes the proxy militias it has established and societal changes it has begun are enough to secure its interests in Syria, it may be willing to significantly reduce its military presence. Internationally, a Syrian return to the Arab League would also give Iran influence within regional Arab diplomacy. Economically, Iran would further benefit from a less-isolated Syria that is better able to pay back the debts it accrued to Iran during the war. Additionally, leaving military activities to militia proxies would free up IRGC resources. Iranian military bases could be handed over to militia proxy control instead of returning to the Syrian army. This could allow a rapid IRGC return to the military positions it built up in Syria if it ever decided to so.
Despite the benefits, any significant IRGC military withdrawal is highly unlikely in the short term. The security environment is still too unstable for Iran, particularly in strategic locations such as Deir ez-Zor, where IS cells still operate and the U.S. maintains a military presence. Iran is likely to seek to undermine both rivals before any real military reduction occurs. Iran has already increased attacks targeting U.S. military bases toward the end of 2021 to achieve this goal, while security operations targeting IS have continued.  Iran would also favor a gradual drawdown of IRGC troops since the long-term loyalty of the militias it has built up still remains unproven. This is particularly the case in Deir ez-Zor, where Iran was able to co-opt a local Sunni population due to long-term economic and political marginalization of the region by Assad’s regime and the ongoing security vulnerability caused by IS.
While Iran is likely to support Syria’s attempts to normalize relations with the Arab world, there remain risks to Iran’s influence in Syria even with a long-term and gradual withdrawal of its presence. Increasing Gulf state influence in the country could be aimed at building cultural institutions and community outreach projects of its own. Such projects could seriously undermine Iran’s influence, particularly in Sunni majority areas, given that it is unclear how sincere domestic Sunni buy-in has been to Iranian cultural and religious infiltration.
This could set off an intense Iran-Gulf state competition for Syrian loyalty, with each side pouring more and more money into attracting Syrians to their spheres of influence. This, in turn, would contribute to the fragmenting of an already weakened Syrian national identity. The possibility of renewed conflict would also increase, particularly if Gulf state projects in the country are based on supporting a Sunni Islamist identity to counter the Shia Islamist identity built by Iran. IS would also likely ride the wave of increased sectarianism to expand recruitment activities, further undermining Syria’s stability.
 See Danny Makki, “The UAE paves way for Syria’s return to the Arab fold, but plenty of hurdles remain” (The Middle East Institute, January 2022).
 See Christopher Phillips, The Battle for Syria, pg. 160, (Yale University Press, April 2020).
 See Afshon Ostovar, Vanguard of the Imam, pg. 205-218, (Oxford University Press, April 2016).
 See Hamidreza Azizi, “Iran’s Multi-Faceted Strategy in Deir ez-Zor (SWP, March 2020).
 See Phillips, pg. 162.
 See Navvar Saban, “Factbox: Iranian presence in Syria’s Deir ez-Zor province” (Atlantic Council, May 2021).
 See Phillips, pg. 158.
 See Ziad Awad, “Iran in Deir ez-Zor: Strategy, Expansion, and Opportunities” (European University Institute, February 2020).
 See Steven Heydemann, “Assad’s normalization and the politics of erasure in Syria”, (Brookings, January 2022).
 See “Operation Inherent Resolve Quarterly Report October 1-December 31, 2021” (U.S. Department of Defense, February 2022).