US-Iranian Tension in Eastern Syria: Causes and Prospects

EPC | 04 Aug 2021

Tensions have recently escalated between US forces and Iranian militias in eastern Syria against the backdrop of an uptick in attacks by Iranian militia on US bases in Iraq and Syria, and counter-raids by US forces against Iranian militias. The two sides have been using the Syrian arena to settle scores and send political and military messages, which increases the complexity of the situation in the Arab country and threatens a military clash between these parties. This paper examines US-Iranian tension; its causes and trajectories.

Context and Dynamics

On June 27, 2021, US forces launched airstrikes against Iranian-backed militias in Syria and Iraq, under the direction of President Joe Biden, in response to these militias targeting US forces in Iraq. The sorties targeted operational facilities and weapons depots in two locations in Syria and one in Iraq, affiliated with Kata’ib Hezbollah and Kata’ib Sayyid al-Shuhada.

The targeted militias vowed to retaliate against the American forces for these raids. Indeed, the response was not long in coming. On June 28, a US military base in the "Al-Omar" oil field, which houses the largest US military base in eastern Syria, was subjected to missile attacks. Despite the American bombing of Iranian militias in areas west of the Euphrates in Syria, the Iranian militias' attacks against the "Al-Omar oil field" and "Koniko gas field" continued unabated. The Pentagon expressed concern about the continuing attacks. Its spokesman, John Kirby, said "they are using lethal weapons and this is a serious threat".

This tension comes at a time when the two sides are working to adjust their strategies towards each other. On the one hand, the Biden administration's strategy is based on showing that the United States is resolute against its rivals in various international arenas. As for Iran, the Biden administration changed its policy toward the threats of Iranian-backed militias from merely responding if an American military was killed in an attack, which is the strategy pursued by the Trump administration, to retaliating only just because those militias attacked American forces1. Indeed, the Biden administration did not hesitate to launch airstrikes on Iraqi militias since its first days in the White House, although some in Washington believe that they are "small and light" strikes, indicating the US administration's desire to avoid escalation.2

On the other hand, the Iranian strategy aims to harass US forces and force the US administration to consider withdrawing its forces from Syria, as well as establishing new rules of engagement so that Washington must expect a military response every time. However, Iran has been keen to remain behind the scenes, denying its support or knowledge of those who mount these attacks against American forces in order to avoid a direct confrontation with the US.3

However, the US is well aware that Iran is behind these attacks. The Pentagon spokesman, John Kirby, accused "Iranian-backed militias" of carrying out “numerous attacks against American forces in Iraq and Syria," adding that Iran should “cease the support it provides to these militias," and stressed the "US's right to defend itself".Meanwhile, Iraqi sources revealed that Iran had incited Iraqi militias to target US forces in Syria and Iraq, after a visit to Baghdad by the head of the Revolutionary Guards' intelligence, Hossein Taeb, and his meeting with a number of leaders of Iraqi armed factions. It has been reported that Taeb conveyed a message from Supreme Leader Khamenei to these factions calling on them to continue putting pressure on the American forces in Iraq until they leave the region.4

Military Deployment Map

The American and Iranian sides are adjacent to each other in eastern Syria, separated only by the Euphrates River. The American forces are stationed east of the river, while Iranian militias are positioned to the west. The irony is that the Iraqi territories constitute the strategic depth for both of them and the logistical outlet that provides the forces of both parties with equipment and personnel. While the majority of US weapons depots and army supply points are located in Erbil (West Qayyarah base), and in Anbar (Ain al-Assad base), which are close to the Syrian border, Iran controls the Iraqi border areas with Syria, and its militias have absolute control over the Qaim district and its border post with Syria, through which all Iranian supplies to its sites and militias in Syria pass.

I: US Bases

1. In Deir ez-Zor:

The "Al-Omar Oil Field" Base, the largest US military base east of the Euphrates River, is located 10 km to the north-east of the city of Al-Mayadin, at the Omar field (the largest oil field in Syria), and houses a number of Humvees and surveillance systems. It has 12 combat helicopters, a helipad, and a drone landing pad.5 The base is considered the main center for the international coalition to provide air support and to strike Iranian militias in locations on the opposite side, such as Al-Mayadeen, Al-Quriya, Al-Ashara and Mohassan. Recently, the international coalition has expanded the Al-Omar field base, and in recent months hundreds of trucks loaded with ammunition, weapons and logistical materials arrived there. Also, the Al-Omar oil field is relatively close to the areas where Iranian-backed militias are deployed, and it is therefore easy to target with rocket-propelled grenades, and even drones, as happened on the 28th of June. Added to this is the relatively large number of troops present in this base, which gives any attack, even if it is not accurate, a greater chance of inflicting losses among these forces.6

The Koniko Gas Field Base. This base is located 20 km east of Deir ez-Zor city, and was established to protect the Konico gas field. This base has combat vehicles and a helipad.7 It is equipped with a "Patriot" missile system, in addition to a number of modern ”Bradley Fighting Vehicles”. This base is close to the towns of Khasham and Murat, which are under the control of the Syrian regime, and it is only two kilometers away from points where the regime forces are deployed.8

The Baghouz Base. It is a small base in the far southeast of Deir ez-Zor city, close to the Al-Bukamal border crossing with Iraq, which is controlled by the Iranian Revolutionary Guards. Built on the eastern bank of the Euphrates River on a small hill called Al-Baghouz, the base is tasked with monitoring the Iranian Revolutionary Guard and its militias, and it is equipped with armored vehicles and surveillance systems.9

The Al-Susah Base. Built on the northwest side of the Baghouz base, 3 km from the town of Al-Susah, this base monitors the west bank of the Euphrates River, where the Iranian Revolutionary Guards are deployed. The base is equipped with tanks and Humvees and an Apache helipad.10

The Hajin Base. This base is located near the village of Hajin, in the railway building on the eastern bank of the Euphrates. It is tasked with monitoring the movements of Iranian forces and affiliated militias deployed on the western bank of the Euphrates River. It is equipped with armored vehicles and surveillance gear.11

The al-Tanak Oil Field Base. This base is located in the northeast of the village of Umm Hamam in the Al-Mayadin region in the Al-Shaitat desert, near the Al-Tanak oil field, which is the second-largest oil field in Syria. The mission of this base is to protect the field, and it houses a number of Humvees and observation and surveillance equipment. It is equipped with a helipad and 4 combat helicopters.12

The Al-Jufra Oil Field Base. Located in the southeast of Deir ez-Zor city, the mission of this base is to protect the Jufra oil field. It is supplied with armored Humvees and heavy transport vehicles, as well as surveillance and reconnaissance equipment.13

2. In Al-Hasakah:

The al-Shaddadi Base. Built near a gas plant located 1 km southeast of the outskirts of the town of Al-Shaddadi, south of Al-Hasakah, this base contains a helipad, a drone runway, a training camp, a mini-operations room, and at least 8 combat helicopters.14

The Tal Hajar al-Rumailan Base. This base is originally an agricultural airport converted by US forces to be used by helicopters and drones of all kinds. It was also rehabilitated to receive medium-sized cargo planes. The base plays a pivotal role after the redeployment of US forces in Syria. It houses large number of combat equipment, including tanks, fighting vehicles, combat helicopters, transport vehicles, drones, and reconnaissance, and communication equipment. It is considered the main base after the American forces evacuated their bases in the provinces of Raqqa and Aleppo.15

The Khabour Dam Base. Built near the Khabour Dam, southeast of the city of Hasakah, this base has ground and air support forces, in addition to a number of support helicopters and airdrops.16

3. In Raqqa:

The Al-Jazarah Base. West of Raqqa city, the mission of this base is to protect the sugar factory base, and to provide logistical support to the SDF forces in the area. It is equipped with armored personnel carriers, minesweepers and pickups.17

Regarding the deployment of US forces in Syria, the following is noted:

  • The number of US bases in Syria exceeds twenty.
  • The US bases are located in eastern Syria, more than 90 miles (150 km) from Deir ez-Zor to the border area east of Al-Hasakah.
  • The deployment of forces shows a geographical field link between many sites, such as the network linking the American presence in Al-Anbar, Iraq, Al-Tanf, southwest of Al-Qaim and Al-Bukamal, as well as in Rumailan, east of Al-Hasakah, with bases in Dohuk in Iraqi Kurdistan, and with the Sinjar base as well. 

II: Iranian Deployment

The Imam Ali Base. Located in the Al-Hari area in the vicinity of Al-Bukamal, this base has 15 military points, including 10 that contain a number of weapons depots and yards for training fighters, in addition to a number of military headquarters for the Iran-backed militias, led by the Iranian Revolutionary Guards and the “Fatimiyoun” militia, in addition to the Quds Force. There are also five other points supplied with advanced missile launchers. This base is considered the largest Iranian military base that Iran has built in Syria, and the most important in geostrategic terms. It is very close to the Iraqi border, and can serve Iran's goals in both countries, due to its proximity to the Al-Qaim border crossing, vital for funneling weapons and missiles to Syria.18

The Al-Ward Oil Field Base. Located in the vicinity of Al-Bukamal, this base is occupied by the Iraqi al-Nujaba Movement, the Popular Mobilization Forces, and a number of other Iranian militias.

The Military Headquarters Complex in Al Jalaa. It is a compound housing Iranian military points and headquarters in the Al-Jalaa region, near the archaeological site of "Dura-Europos" in the vicinity of Al-Bukamal. The Iranian militias present in this complex carry out continuous support missions and patrols in the cities of the eastern countryside of Deir ez-Zor Governorate.

The T2 or Al-Kum Base. It is located in the desert opposite the city of Al-Bukamal, which is the closest to the American bases, and close to it also there is a last pocket of the "ISIS".

The Deir ez-Zor Military Airport Base. It is a base shared by Iranian-backed groups, led by "Hezbollah", and Russian army units.

The Al-Saika and Talae'a Camps Bases. These bases are the largest concentration of Iranian militias inside the city of Deir ez-Zor, and are located near the governorate building and the Al-Jura neighborhood. In general, they serve as training and gathering camps for militia fighters and a launchpad towards the central region.

The Ain Ali Base. It is located in the desert of the city of Al-Quriya in the eastern countryside, and the "Fatimiyoun" militia established a religious shrine in it. In addition to the importance of this point militarily, it is also a center for the gathering of pilgrims from Iran and Iraq towards Syria.19

The number of Iranian sites and points in the Deir ez-Zor region is close to 13. Iran has recently brought advanced weapons to its bases in eastern Syria, especially to the "Imam Ali" base. It also deployed short-range "Katyusha and Grad" missiles and medium-range "120 mm" artillery at its military points and headquarters in the western countryside of Deir ez-Zor.20

Iranian Motives and American Confusion

Although the uptick in attacks targeting American forces in eastern Syria indicates the activation of a strategy that the Syrian regime has alluded to more than once, in terms of establishing a "popular resistance" front against the American presence, Iran and its militias have adopted this strategy and merged it with the “Iraqi Front” opposing the American presence, which was formed especially after the assassination of the Iranian Quds Force commander Qassem Soleimani early last year21. However, reality does not prove this matter, for more than one reason:

  • Despite all that Iran has done to recruit tribesmen in eastern Syria, the facts confirm that these forces cannot be relied upon to confront the American forces, due to the tribes' exhaustion and weakness. Nor are these forces intended to fight US forces, but rather for local goals to subjugate the local population to the Iranians.
  • In those areas, a popular incubator for the resistance against the Americans did not form. Those areas are occupied by Iranian militias who confiscate the property of the local population and seek to change their beliefs, and they do not have any feelings of anger towards the Americans.
  • It is no longer a secret that Iraqi and Afghan militias are targeting US forces, and these attacks, although limited, cannot be continued for a long time because they are costly. The militias that carry them find themselves compelled every time to redeploy, camouflage and hide among the people's homes at a time when no losses are recorded on the American side.

Based on the latest developments, it is possible to identify the motives behind Iran's escalation with the United States and employing it to secure political returns on more than one front:

Send messages before returning to the Vienna negotiations: The Iranian escalation indicates that the Vienna negotiations on sanctions imposed on Iran and its nuclear program have stumbled. It is likely that the Americans set conditions that Iran does not want to accept. At the same time, Iran is aware that there are conflicting voices within the Biden administration regarding the negotiations, so it is trying to push the US administration, especially those eager to negotiate with Tehran, to speed up the negotiations and not give the Iranian hardliners an opportunity to derail the talks22.

Pre-empty any possible Russian-American agreement: It goes without saying that Iran was not happy about the Russian-American rapprochement over Syria, because it believed that these understandings would limit its influence in Syria, in light of international demands that Iran be removed from that Arab country. The US-Russian coordination regarding the continuation of aid delivery through the Bab al-Hawa crossing, as well as Washington and Moscow's assertion of the existence of other understandings between them on Syria, constituted a wake-up call for Iran, especially if things moved towards implementing the international resolution 2254, which requires the removal of foreign militias from Syria and their disengagement with Iran23. Accordingly, Iran is trying to reformulate the situation in Syria in a different way based on creating popular resistance against the US military presence, and perhaps Russia in the future. Iran wants to control this potential resistance, and at the same time claims that it has nothing to do with these local dynamics that occur in a natural context as resistance to the occupation, and thus Tehran can shuffle the cards forcefully in the face of any US-Russian understandings against it.

Employ US withdrawl from Afghanistan: The US military withdrawal from Afghanistan, in the way it happened, inspires Iranian regional policy planners, who seek to exploit American voices demanding the removal of US forces from the "swamps" of the Middle East in order to avoid losses and not get involved in complex and intertwined issues without a clear strategic horizon. Iran finds in this move an opportunity to force the Americans, who have become highly sensitive to any losses in a region that is no longer very important in their strategic assessments and perceptions, to leave and clear the arena for Iran.24

Although the US forces launched strikes against Iranian militias in Syria, the matter revealed confusion within the US administration, especially in Congress, which was divided between supporters of the need to maintain the powers that allow the executive branch to strike targets in Syria and Iraq, and those who oppose it25. President Joe Biden's policy is to use "absolute minimum" force to deter pro-Iranian militias in Iraq and Syria, while Republicans are demanding a maximum force response to this type of attack.

The confusion of the Biden administration reveals its unwillingness to go far in responding to the Iranian moves, so as not to reflect on the negotiations between the two parties, which seem to be an additional brake on the administration. This is in addition to the US administration's desire not to get involved in new wars at a time when President Biden made his choice to stay away from foreign wars and withdrew the US forces from Afghanistan26.

However, it appears that the Biden administration is not considering withdrawing from Syria at this stage, which appears to be excluded from plans to reduce US forces in the Middle East. This may be due to the fact that the US administration is keen to support the Kurdish Autonomous Administration in Syria, and not to allow Iran and its militias to penetrate further into eastern Syria and tighten their grip on it, which will have catastrophic repercussions not only on American interests but also on strategic allies in the region, foremost of which is Israel.27

Summary and Conclusions

The escalation between US forces and Iranian militias in eastern Syria is an opportunity for the Iranians to prove that they are an active and essential stakeholder in the region, and have the ability to create dynamics that confuse other actors. On the other hand, the US administration seems confused as a result of the many determinants that restrict its actions towards what can be called "Iranian harassment" and consequently limit its ability to restrain these parties. As a result of this confusion, Iran is already seeking to change the rules of engagement in the region. It is trying to impose new facts on the ground based on the fact that what is happening is nothing but popular resistance to an American occupation, so that this "resistance" will turn into an Iranian card not only against the Americans, but also against the Russians and perhaps the Turks in the future.

However, Iran realizes that its tools are insufficient in this confrontation, the most important of which is the hostile environment it faces in those areas, which will not give it the opportunity to create a popular incubator for resistance against the Americans. It also understands that the United States uses only a fraction of its power. Therefore, the most that Iran can aspire to at this stage is to push the Americans to reposition and deploy their forces, as happened when Turkey invaded areas of northern Syria in October 2019, or what was called at the time “Operation Peace Spring”, which would allow the deployment of Iranian forces in areas near their bases, especially in the Al-Omar oil field.

It does not seem that this matter is achievable, due to the insistence of the US administration to stay in the areas of eastern Syria, which is the key to Iranian control of the region. This is in addition to that Russia itself will not be ready to recognize Iranian influence in that region, and this may be a motive for concluding Russian-US understandings to prevent Iran's expansion into this region.

It is unlikely that things will develop further in the areas east of the Euphrates to more than they are currently, i.e. just light strikes by two sides whose realistic calculations push them to calm down as much as possible. On the one hand, Iran, with its current tools, cannot do more than that, and realizes that any extra step in the conflict with the Americans would greatly affect its most important project, which is to turn Syria into a long-term sphere of influence. On the other hand, the United States is not interested in a "high-level" escalation that would affect its plans to reduce its presence in the Middle East.


  1. Washington wanted to send a message to Iran that there is no immunity from punishment, Biden’s “dual” strategy towards Iran - The UAE Al-Watan newspaper, March 2, 2021. (Arabic)
  2. Biden Wants to Leave the Middle East, But He’s in a Vicious Bombing Cycle in Iraq - Michael Knights, The Washington Institute, July 2, 2021.
  3. Adnan Ali, “What is the purpose of the attacks on American bases in Syria?” - Syria TV, July 14, 2021. (Arabic)
  4. Reuters: Iranian commander urged escalation against US forces at Iraq meeting, sources say, June 13, 2021.
  5. Bassam Jumaida, “US Military Bases in Syria… Location and Role” - Oman Newspaper, July 1, 2020. (Arabic)
  6. Adnan Ahmed, “Al-Omar Oil Field in Syria is Now the Target: Political and Economic Messages to Washington” - Al-Araby Al-Jadeed, July 11, 2021. (Arabic)
  7. Saleh Al-Dahni, “The oil fields that America announced to remain in Syria to guard” - Arabi21, October 28, 2019. (Arabic)
  8. Adnan Ahmed, “Al-Omar Oil Field in Syria is Now the Target...” A previous source.
  9. “What are the locations of the new US bases around the Deir Ezzor oil fields?” - Al-Quds Al-Arabi, November 5, 2019. (Arabic)
  10. “The international coalition forces continue to fortify the base they established near Al-Susah” - The Syrian Observatory for Human Rights, September 7, 2018. (Arabic) 
  11. “Despite Trump’s decision to withdraw… a new American base in Hajin” - The Syrian Observatory for Human Rights, December 20, 2018. (Arabic)
  12. Saleh Al-Dahni, “The oil fields that America announced to remain...” A previous source.
  13. "The American army is repositioning its forces in Syria" - Anadolu Agency, November 9, 2019. (Arabic)
  14. "Al-Hasakah... New photos of a US military base in "Al-Shaddadi" - Zaman Al-Wasl website, December 18, 2017. (Arabic)
  15. “US Military Bases in Syria… Location and Role” A previous source.
  16. "Al-Hasakah... “New photos of a US military base in "Al-Shaddadi” A previous source.
  17. “American forces stationed west of Raqqa after withdrawing from border areas” - Anadolu Agency, November 2, 2019 (Arabic)
  18. Imad Karkas "The Expansion of Iranian Activity in Eastern Syria: Military Bases and Religious Activities" - November 25, 2019 (Arabic)
  19. Khaled Al-Mutlaq, “Iranian military bases and the beginnings of its security and military intervention in Syria” - Harmon Center for Studies, May 16, 2020. (Arabic)
  20. Kamal Sheikho, “A fourth attack targeting the American army in eastern Syria” - Al-Sharq al-Awsat newspaper, July 12, 2021. (Arabic)
  21. Adnan Ali, “What is the purpose of the attacks on American bases in Syria?” - Syria TV, July 14, 2021. (Arabic)
  22. Why did Iran’s militias escalate against the American forces in Syria?, Baladi News, July 13, 2021. (Arabic)
  23. Tony Francis, “The U-turn by Moscow and Washington in the Security Council, Iranian Tension Reflects in Inflammation Points of Influence, and Damascus Rejects the Russian Decision” - Independent Arabia, July 12, 2021. (Arabic)
  24. Why did Iran’s militias escalate against the American forces in Syria?” A previous source.
  25. Igor Sobotin, “They urge Biden not to abandon Syria and Iraq” - Russia Today, July 12, 2021. (Arabic)
  26. Victor Shalhoub, “Biden between pressures and restrictions to confront militias in Syria and Iraq” - Al-Araby Al-Jadeed, July 13, 2021. (Arabic)
  27. Biden administration excludes Syria from plans to reduce its forces in the region - Al-Arab, July 13, 2021. (Arabic)

Latest Featured Topics