Dangerous Liaisons: Russian Cooperation with Iran in Syria

The Issue

As tensions escalate between the United States and Iran in the Middle East, Russia is engaged in covert and overt cooperation with Iran in ways that undermine U.S. national security interests. This analysis of commercial satellite imagery at Tiyas Airbase in Syria indicates the scope and proximity of Russian and Iranian military ties. If Washington wants to contain Tehran and prevent further Iranian expansion, U.S. policymakers will need to increase pressure on Moscow to curb Tehran’s activities in countries like Syria.


Following a June 2019 meeting with Iranian President Hassan Rouhani at the Shanghai Cooperation Organization summit in Kyrgyzstan, Russian President Vladimir Putin remarked that “relations between Russia and Iran are multifaceted, multilateral.” In characterizing the primary areas of cooperation, Putin noted: “this concerns the economy, this concerns the issues of stability in the region, our joint efforts to combat terrorism, including in Syria.”1 One example of Russian-Iranian cooperation is in Syria.

This brief analyzes satellite imagery of Tiyas Airbase (or T-4) in Syria, which is used by Iran and Russia. It highlights what we assess to be the Iranian movement of weapons, other material, and personnel to Syria with the awareness and support of Moscow. This cooperation, which has allowed Iran and its Islamic Revolutionary Guard Corps-Quds Force (IRGC-QF) to increase their capabilities and influence in Syria, should be concerning for the United States as tensions increase between Washington and Tehran. Yet Moscow’s cooperation with Tehran is double-edged. Our analysis also highlights Israeli attacks against Iranian or Iranian-linked targets at T-4 Airbase in close proximity to Russian aircraft. These developments suggest that Moscow is playing a delicate game in Syria. It supports Iranian activity and aid in Syria, but also explicitly or tacitly allows Israeli military actions against Iranian targets.

The rest of this brief is divided into four sections. The first provides an overview of Russian-Iranian relations. The second section analyzes satellite imagery of T-4 Airbase, focusing on the possible Iranian movement of arms, other material, and personnel. The third section highlights Israeli airstrikes in Syria, including at T-4 Airbase, in close proximity to Russian aircraft. The fourth provides a brief conclusion.

Russian-Iranian Partnership in Syria

Russia and Iran have developed a complex—and sometimes contentious—historical relationship. During World War II, for example, the Soviet Union occupied northern Iran, creating deep suspicion and mistrust among many Iranians.2 Yet Moscow and Tehran have developed a working relationship in Syria, even though they have their own interests.

Moscow’s decision to become directly involved in the Syrian civil war—including to work with Iran—was motivated by several concerns. First was a growing fear that Washington was preparing to overthrow the Assad regime and replace it with a friendly government, much like the United States had done in Afghanistan in 2001, Iraq in 2003, and Libya in 2011.3 The possibility of losing Syria was particularly alarming because Moscow had just lost its ally in Ukraine. The 2014 Ukrainian revolution had ushered in a pro- Western government in Kiev, further fueling Russian fears of U.S. activity. Second, Syria had long been an important ally of Moscow. In 1946, the Soviet Union supported Syrian independence and provided military assistance to the Syrian Arab Army. This cooperation continued during the Cold War and endures under Russian President Vladimir Putin today.4 Third, Russian leaders were concerned that Assad’s collapse would allow the Islamic State, al-Qaeda, and other terrorists to use territory in Syria and Iraq to attract more fighters, improve their capabilities, and spread terrorism in and around Russia. After all, over 9,000 individuals from Russia, the Caucasus, and Central Asia traveled to Syria and Iraq to join Salafi-jihadist groups like the Islamic State and al-Qaeda.5

Iran has its own interests in Syria. Following the onset of the Syrian civil war in 2011, Iranian leaders became alarmed at the rise of Sunni extremist groups like the Islamic State and U.S., European, and Gulf support to rebel groups.6 In addition to providing light and heavy weapons to the Syrian regime and militias, up to 3,000 Islamic Revolutionary Guard Corps-Quds Force (IRGC-QF) helped plan and execute campaigns such as the 2016 Battle of Aleppo (or Operation Dawn of Victory).7 The IRGC-QF worked closely with the Assad regime and the Russian military, which conducted strikes from Russian combat aircraft and naval vessels in the Mediterranean Sea.8 Syrian forces and militias supported by the IRGC-QF shelled rebel positions in Aleppo as Russian close air support and Kalibr cruise missile strikes reduced entire neighborhoods to rubble. By December 2016, ground forces routed rebel forces, who departed under an agreement brokered by Russia, Turkey, and Iran.9 Iranian support continues today.

In addition, Iranian leaders have tried to use their activity in Syria to counter Israel. Perhaps the most significant example is by encouraging the expansion of Lebanese Hezbollah and other militia groups in Syria. Lebanese Hezbollah deployed up to 8,000 fighters to Syria and increased its arsenal with greater numbers and ranges of rockets and missiles from Syrian territory.10 Hezbollah also trained,  advised, and assisted Shia and other non-state groups in Syria. Today, the IRGC-QF works with thousands of trained fighters in Syria operating in local militias. Many of these groups like Lebanese Hezbollah possess advanced stand-off weapons, improved cyber capabilities, more recruits, and more expansive forces in Syria capable of striking Israeli targets.

While Russian-Iranian cooperation has been contentious at times, both countries have collaborated in Syria in ways that serve their own interests. One example of this cooperation is at T-4 Airbase, which is located in eastern Homs Governorate and roughly 100 miles northeast of Damascus.

T-4 Airbase and Flight Tracker Data

Figure 1 shows the base using satellite imagery. On the east side of the base is an apron (ramp) where aircraft, helicopters, and unmanned aerial vehicles (UAVs) are frequently parked. On the west side is an apron where transport aircraft have been located and where Israeli aircraft have struck targets.

Figure 1: T-4 Airbase

Satellite imagery in Figure 2 highlights a Russian-made Ilyushin Il-76-MD cargo aircraft on the base. This aircraft is likely the former Russian Airforce Il-76 registered RA-76634, as indicated by the number painted underneath the cockpit and livery of the aircraft.11 The imagery shows the freighter being loaded or unloaded under the protection of multiple Syrian air defense systems, including three SA-2 systems and a Pantsir-S1— all of which were provided by Russia.12

We assess that the Il-76 and other commercial aircraft may have been used to transport weapons, other material, or personnel from Iran into Syria, based on the regular use of Il-76s for these purposes in Syria.13

Figure 2: Il-76 on T-4 Runway

Flight tracker data of the Il-76 aircraft indicates a recent history of flights between Tehran and Damascus. As indicated on the wing, the plane is registered as YK-ATD. The Prefix (YK) is the Syrian country code. Other Syrian-owned Ilyushin Il-76 aircraft have similar registry codes, such as YK-ATA, YK-ATB, and YK-ATC. Publicly available flight tracker data indicates the YK-ATD makes regular flights between Tehran and Damascus. As illustrated in Figure 3, on May 13, 2019, YK-ATD departed Damascus International Airport. On May 14, 2019, the day we observed YK-ATD at T-4 Airbase, flight records indicate the plane left Tehran Mehrabad International Airport in the morning, arrived at what we assess to be T-4 based on imagery analysis, and then departed for Damascus International Airport in the afternoon. Our analysis of flight history for other Syrian-owned Il-76 aircraft indicates similar flight patterns between Iran and Syria for other aircraft, possibly for the purpose of clandestinely transferring weapons, other material, and personnel into Syria.14

Figure 3: Flight Data Tracker Map for YK-ATD

As shown in Figure 4, we identified four Russian fixed-wing Su-25 ground attack aircraft with full weapons loads at the same site as the Il-76 aircraft, as well as an Mi-17 Hip transport helicopter and an Mi-24 Hind attack helicopter.15 The proximity of Russian aircraft to the Il-76 suggests that Russia was highly likely aware of Iranian activity. It is virtually inconceivable that Iran would transport and unload arms, other material, and personnel to a base frequented by Russian aircraft and government officials—and protected by Russian-made air defense systems— without Moscow’s knowledge and approval.

Figure 4: Russian Su-25, Mi-24, and Mi-17 Aircraft on Runway

The imagery also indicates three active air defense sites around the perimeter of T-4 Airbase. Figure 5 highlights one of these sites. All of the air defense sites are equipped with Russian-made weapons systems. The first SA-2 air defense site is situated to the north, another SA-2 air defense site is located to the northwest, and a third SA-2 air defense site is to the south. The SA-2 Guideline (Russian designation S-75 Dvina) is a high-altitude, command guided, surface-to-air missile system (SAM) capable of 360-degree coverage. The SA-2 Guideline is designed for the defense of fixed targets and field forces.16 The guidance system of an SA-2 site can only focus on one target at a time but can direct three missiles against a target simultaneously.17 This likely explains the need for multiple SA-2 systems around the airbase.

Figure 5: SA-2 Air Defense System

Also observable in the imagery is a Pantsir-S1 (NATO name—SA-22 Greyhound) transloader. The Panstsir-S1 is a short- to medium-range missile and anti-aircraft artillery weapon produced by Russia. The Pantsir-S1 provides point air defense for various installations and provides protection to air defense units. Figure 6 illustrates the Pantsir-S1 air defense system.

Figure 6: S-1 Pantsir Air Defense System

All military assets in the imagery are Russian made. We assess that the YK-ATD was likely either leased or sold to Syria.18 The Su-25 combat aircraft, as well as the Mi-17 and Mi-24 rotary-wing craft, are likely Russian operated.19 The SA-2 Guideline and Pantsir-S1 are Russian-built SAM systems.20These air defense systems are just two of numerous air defense systems provided by Russia to the Assad government. Others include S-75s, S-200s, S-300s, and Strela-1/-10s.21

With Russian support, Iran has used these types of activities to expand its presence in Syria. Today, the IRGC-QF works with thousands of trained fighters in Syria who are operating in local militias, including Lebanese Hezbollah. The 2006 Israel-Hezbollah War demonstrated Israel’s difficulty of rooting out Hezbollah sites in Lebanon. Iran’s activity in Syria has only expanded the nature of this problem for Israel’s military.

Israeli Airstrikes in the Shadow of the Bear

Despite Russia’s collaboration with Iran, Moscow has also attempted to placate Israeli concerns about Iranian expansion. This section highlights Israeli attacks against Iranian or Iranian-linked targets—including at T-4 Airbase in close proximity to Russian aircraft. These developments suggest that Moscow supports Iranian activity and aid in Syria, but also condones some Israeli military actions against Iranian targets. Russia and Israel have established deconfliction mechanisms, including a hotline between the Israeli and Russian militaries. As one Israel Defense Force official remarked, “We are very strict about informing the Russians about our activities and that their operational picture is up to date.”22 This cooperation is particularly important to avoid incidents like the one in September 2018. Following an Israeli strike against Iranian-linked targets in western Syria, Syrian gunners accidentally shot down a Russian IL-20 surveillance aircraft. Russia complained that Israel had given Russian leaders less than a minute of advanced warning and Israeli aircraft used “the Russian airplane as a cover.”23 Despite some improvements in cooperation, Russia has occasionally condemned Israel for its actions in Syria. In July 2019, for example, Russia publicly criticized a series of Israeli strikes, saying that that they “grossly violate[d] Syria’s sovereignty.24

Figure 7 plots the location of Israeli airstrikes against Iranian and other targets in Syria. The darker shades of blue in the heat map indicate a higher concentration of Israeli strikes. Most of Israel’s attacks have been in southwestern Syria, near the Israeli border. But a few attacks have been against major bases used by Iran and Iranian-linked groups, including T-4 Airbase, the airbase north of al-Qusayr, and Damascus International Airport.

Figure 7: Israeli Strikes in Syria

On June 2, 2019, Israel conducted an airstrike on T-4 Airbase.25 This strike, along with similar strikes conducted in 2019, indicate that Israel is still committed to contesting attempts by Iran to entrench itself and its non-state partner forces in Syria. As highlighted in Figure 8, satellite imagery taken before and after the Israeli airstrike indicates that a UAV control vehicle, launch ramp, and ground equipment were likely targeted. This airstrike, which was conducted in close proximity to Russian infrastructure on the base, highlights the ongoing challenge Israel faces when conducting strikes near Russian forces.

Figure 8: Before and After Imagery of Israeli Strike Against Iranian-Linked Target at T-4


The Trump administration has expressed significant concern about Iran’s nuclear ambitions, its missile program, and the activities of the IRGC-QF and its partner forces in the Middle East. One of the countries where Iran has been most active is Syria, where Tehran has increased its military presence to aid the Assad regime; supported Lebanese Hezbollah, which has been directly involved in the Syrian ground war; and expanded the number of rockets and missiles in the country to establish a second front (along with Lebanon) in a future war with Israel.

Yet Iranian actions in Syria have been possible, in part, because of Tehran’s cooperation with Moscow. Containing Iran and preventing further Iranian expansion in the Middle East will be difficult without increasing pressure on Moscow. If Washington wants to be more effective in containing Iran, U.S. policymakers need to put greater pressure on Moscow to curb Tehran’s movement of arms, material, and people— as this case study of T-4 Airbase highlights.

Seth G. Jones holds the Harold Brown Chair, is director of the Transnational Threats Project, and is a senior adviser to the International Security Program at the Center for Strategic and International Studies (CSIS) in Washington, D.C. Nicholas Harrington is a research assistant and program coordinator for the Transnational Threats Project and the Arleigh A. Burke Chair in Strategy at CSIS. Joseph S. Bermudez Jr. is a senior fellow for Imagery Analysis at CSIS.

The authors give special thanks to Brian Katz and Danika Newlee for their helpful comments

This brief is made possible by general support to CSIS. No direct sponsorship contributed to this brief.

CSIS Briefs are produced by the Center for Strategic and International Studies (CSIS), a private, tax-exempt institution focusing on international public policy issues. Its research is nonpartisan and nonproprietary. CSIS does not take specific policy positions. Accordingly, all views, positions, and conclusions expressed in this publication should be understood to be solely those of the author(s).

© 2019 by the Center for Strategic and International Studies. All rights reserved.

1Quoted in Tom O’Connor, “Russia Praises Iran and Their Joint Wins in Syria as U.S. Tensions Rise,” Newsweek, June 14, 2019, https://www.news- week.com/russua-praises-iran-syria-us-1444041.
2Amin Saikal, Iran Rising: The Survival and Future of the Islamic Republic (Princeton, NJ: Princeton University Press, 2019), 225.
3See, for example, Sergei Lavrov, “On Syria and Libya,” Monthly Review, May 17, 2011, https://mronline.org/2011/05/17/on-syria-and-libya/. The text is an excerpt from “Transcript of Russian Foreign Minister Sergey Lavrov’s Interview to Russian Media Following Attendance at Arctic Council Meeting, Nuuk, May 12, 2011,” published on the Russian Foreign Ministry website, May 13, 2011.
4Byron Tau, “Obama Renews Call for Assad to Step Down,” Wall Street Journal, February 24, 2015, https://www.wsj.com/articles/obama-renews-call-for-assad-to-step-down-1424804546.
5Richard Barrett, Beyond the Caliphate: Foreign Fighters and the Threat of Returnees (New York: The Soufan Center, October 2017), http://thesoufancenter.org/research/beyond-caliphate/. Also see Thomas Sanderson et al., Russian-Speaking Foreign Fighters in Iraq and Syria: Assessing the Threat from (and to) Russia and Central Asia (Washington, DC: Center for Strategic and International Studies, December 2017), 2, https://csis-website-prod.s3.amazonaws.com/s3fs-public/publication/180726_Russian_Speaking_Foreign_Fight.pdf?VyUdcO2D6TJdW_Zm4JkmIpRkJxoXEZU6.
6International Crisis Group, Iran’s Priorities in a Turbulent Middle East (Brussels: International Crisis Group, 2018), https://d2071andvip0wj.cloudfront.net/184-iran-s-priorities-in-a-turbulent-middle-east_1.pdf.
7On the number of IRGC-QF in Syria see, for example, the data from Gadi Eisenkot, former chief of staff of the Israel Defense Forces, in Bret Stephens, “The Man Who Humbled Qassim Suleimani,” New York Times, January 11, 2019, https://www.nytimes.com/2019/01/11/opinion/gadi-eisenkot-israel-iran-syria.html.
8On IRGC-QF activity, see Seth Jones, “War by Proxy: Iran’s Growing Footprint in the Middle East,” CSIS, March 2019, https://www.csis.org/war-by-proxy.
9On Iranian support to combat operations in Syria see Michael Kofman and Matthew Rojansky, “What Kind of Victory for Russia in Syria?”Military Review (March-April 2018): 6-23; Sanu Kainikara, In the Bear’s Shadow: Russian Intervention in Syria (Canberra: Air Power Development Centre, 2018); John W. Parker, Putin’s Syrian Gambit: Sharper Elbows, Bigger Footprint, Sticker Wicket (Washington, DC: Institute for National Strategic Studies, National Defense University, 2017); Nader Uskowi, Temperature Rising: Iran’s Revolutionary Guards and Wars in the Middle East (Lanham, MD: Rowman & Littlefield, 2018), 77-96; Afshon Ostovar, Vanguard of the Imam: Religion, Politics, and Iran’s Revolutionary Guards (Oxford, UK: Oxford University Press, 2016), 204-229.
10Uskowi, Temperature Rising, 82.
11See, for example: LutwaffeAS, “New IL-75 Syrian Air (leased or donated?) appears with new reg. YK-ATF, it means there is ATE also,” Twitter, May 8, 2019, https://twitter.com/LuftwaffeAS/status/1126038846762881024. This Twitter account monitors Syrian Air Force activity.
12International Institute for Strategic Studies (IISS), “Middle East and North Africa,” in Military Balance (IISS, 2019), 320-379, https://www.iiss.org/publications/the-military-balance/the-military-balance-2019/middle-east.
13Past reporting also indicates flights between Iran and Syria have caused concern for U.S. intelligence officials. See, for example: Barbara Starr, “Recent Iranian Shipments to Syria Concern U.S. intelligence,” CNN, April 25, 2018, https://www.cnn.com/2018/04/25/politics/iran-shipments-syria/index.html.
14See, for example, Starr, “Recent Iranian Shipments to Syria Concern U.S. Intelligence.”
15International Institute for Strategic Studies (IISS), “Middle East and North Africa,” in Military Balance.
16“V-75: SA-2 Guideline,” Federation of American Scientists, June 23, 2000, https://fas.org/nuke/guide/russia/airdef/v-75.htm.
17“V-75: SA-2 Guideline,” Federation of American Scientists.
18Rinat Sagdiev, Maria Tsetkova, and Olena Vasina, “How a Secret Russian Airlift Helps Syria’s Assad,” Reuters, April 6, 2018, https://www.reuters.com/investigates/special-report/russia-flights/. See also, International Institute for Strategic Studies (IISS), “Middle East and North Africa,” in Military Balance.
19The Russians have used Su-25 aircraft to perform airstrikes in Syria. See, for example, “Large IED Factory Destroyed in Idlib by Su-25s,” Russian Ministry of Defense, October 2015, http://syria.mil.ru/news/more.htm?id=12059507.
20International Institute for Strategic Studies (IISS), “Russia and Eurasia,” in Military Balance (IISS, 2019), 166-221, https://www.iiss.org/publications/the-military-balance/the-military-balance-2019/russiaeurasia.
21Sean O’Connor, “Strategic SAM Deployment in Syria,” Air Power Australia, January 27, 2014, http://www.ausairpower.net/APA-Syria-SAM-Deployment.html.
22Quoted in Michael Peck, “Middle East Nightmare: Could Israeli Strikes in Syria Trigger War with Russia?” National Interest, April 6, 2019, https://nationalinterest.org/blog/buzz/middle-east-nightmare-could-israeli-strikes-syria-trigger-war-russia-51082.
23“Russia Blames Israel After Military Plane Shot Down Off Syria,” BBC, September 18, 2018, https://www.bbc.com/news/world-europe-45556290.
24Quoted in “Russia Condemns Strikes in Syria, Blames Israel,” Haaretz, July 2, 2019, https://www.haaretz.com/israel-news/russia-condemns-con-demns-strikes-in-syria-blames-israel-1.7431759.
25Times of Israel Staff, “Israeli Intel Firm: Alleged IDF Strike on Syrian Base Targeted Iranian Drones,”Times of Israel, June 4, 2019, https://www.timesofisrael.com/israeli-intel-firm-alleged-idf-strike-on-syrian-base-target- ed-iranian-drones/.

Seth G. Jones
Senior Vice President; Harold Brown Chair; and Director, International Security Program

Nicholas Harrington