From the 2000s until the fall of the Assad regime, the Islamic Republic of Iran and the Syrian Arab Republic were close strategic allies, and Iran provided significant support for the Syrian Ba'athist government in the Syrian civil war, including logistical, technical and financial support, as well as training and combat troops. Iran saw the survival of the Assad regime as being crucial to its regional interests.Iranian Strategy in Syria , Institute for the Study of War, Executive Summary + Full report, May 2013 When the uprising developed into the Syrian civil war, there were increasing reports of Iranian military support, and of Iranian training of the National Defence Forces both in Syria and Iran.BBC Newsnight, report on Iranian military advisor Hadari, 28 October 2013 'Iran's Secret Army' , From late 2011 and early 2012, Iran's IRGC sent tens of thousands of Iranian troops and Shi'ite foreign paramilitary volunteers in coordination with the Syrian government to prevent the collapse of the regime; thereby polarizing the conflict along sectarian lines.

Iranian security and intelligence services advised and assisted the Syrian military in order to preserve the erstwhile Syrian President Bashar al-Assad's hold on power. Those efforts included training, technical support, and combat troops."Syria's crisis: The long road to Damascus: There are signs that the Syrian regime may become still more violent", The Economist, 11 February 2012. Estimates of the number of Iranian personnel in Syria ranged from hundreds to tens of thousands. Iranian government backed Shia Hezbollah fighters, had taken direct combat roles from 2012 until 2024. From the summer of 2013, Iran and Hezbollah provided important battlefield support for Assad, allowing it to make advances on the opposition.

In 2014, coinciding with the peace talks at Geneva II, Iran stepped up support for Assad. Estimates of financial assistance rendered by Iran to the Ba'athist Syrian government ranged from tens to hundreds of billions of dollars.; syrianef; 24, January 2014Iran Spends Billions to Prop Up Assad , Bloomberg View, 9 June 2015.Borzou Daragahi. "Iran Wants to Stay in Syria Forever." Foreign Policy. 1 June 2018.Outlaw Regime: A Chronicle of Iran's Destructive Activities. U.S. Department of State. November 2018. Pages 11, 39. Tehran's objectives included Shi'ification attempts through forced conversions, Shia missionary activities, establishment of shrines and demographic transformations by bringing in foreign Twelver Shia settlers in regime-controlled territories.

Iranian troops and allied militias on the ground were supported by ballistic missiles and air forces, including armed drones utilizing smart munitions. By October 2018, Iranian drones had launched over 700 strikes on Islamic State forces alone."Iran Admits to Conducting 700 Drone Attacks in Syria." Al Araby. 16 October 2018. Accessed 17 October 2018. At the height of its intervention in 2015–18, an estimated 10,000 IRGC forces and 5,000 Iranian Army members were stationed in Syria alongside tens of thousands of Iranian-led foreign militias. In 2018, 2,000 officers of the Quds Forces commanded an estimated 131 military garrisons and tens of thousands of Iran-backed Shia jihadists across regime-controlled regions. During 2020, Unit 840 played a role in supporting the Assad regime during the Syrian conflict. Their involvement includes training pro-government militias, providing strategic guidance, and establishing a military presence near the Israeli border. This positioning aims to create a strategic advantage against Israel and to support Hezbollah's operations in the region. In 2023, Iran maintained 55 military bases in Syria and 515 other military points, the majority in Aleppo and Deir Ezzor governorates and the Damascus suburbs; these were 70% of the foreign military sites in the country. On December 6, 2024, after severe military setbacks due to a series of rebel offensives, Iran and its proxies withdrew from Syria.

Background

Iran saw the survival of the Syrian government as being crucial to its interest. Its only consistent ally since the 1979 Islamic revolution, Syria provided a crucial route to supply arms for Hezbollah in Lebanon. IRGC presence in Syria had boasted Syria as being Iran's major geopolitical ally, in addition to viewing Bashar al-Assad's Alawite dominated Ba'athist government as a crucial buffer against the influence of Saudi Arabia and the United States.

The Syrian city of Zabadani was vitally important to Assad and to Iran because, at least as late as June 2011, the city served as the Islamic Revolutionary Guard Corps's logistical hub for supplying Hezbollah in neighboring Lebanon. Prior to the civil war, Iran had between 2,000-3,000 IRGC officers stationed in Syria, who helped to train local troops and manage supply routes of arms and money to Hezbollah.

In April 2014, Hossein Amir-Abdollahian, Iranian deputy foreign minister said, "We aren't seeking to have Bashar al-Assad remain president for life. But we do not subscribe to the idea of using extremist forces and terrorism to topple Assad and the Syrian government". Using its increased leverage during the civil war, Iranian government had been recruiting Alawites by setting up Khomeinist religious centers to convert them to Twelver Shi'ism. It had also been attempting demographic shifts by bringing in foreign Shia settlers and families of IRGC soldiers across Syria.

Timeline

2011 In the civil uprising phase of the Syrian civil war, Iran was said to be providing Syria with technical support, based on Iran's capabilities developed following the 2009–2010 Iranian election protests.

In April 2011 U.S. President Barack Obama and U.S. Ambassador to the United Nations Susan Rice accused Iran of secretly aiding Assad in his efforts to quell the protests, and there were reports of Syrian protesters hearing security-force members speaking Persian.

The Guardian reported in May 2011 that the Iranian government was assisting the Syrian government with riot control equipment and intelligence monitoring techniques. According to US journalist Geneive Abdo writing in September 2011, the Iranian government provided the Syrian government with technology to monitor e-mail, cell phones and social media. Iran developed these capabilities in the wake of the 2009 protests and spent millions of dollars establishing a "cyber army" to track down dissidents online. Iran's monitoring technology is believed to be among the most sophisticated in the world, perhaps only second to China.

2012 In May 2012, in an interview with the Iranian Students News Agency which was later removed from its website, the deputy head of Iran's Quds Force said that it had provided combat troops to support Syrian military operations. It was alleged by the Western media that Iran also trained fighters from Hezbollah, a Shia militant group based in Lebanon. Iraq, located between Syria and Iran, was criticized by the U.S. for allowing Iran to ship military supplies to Assad over Iraqi airspace.

Haaretz said that Iran had, by February 2012, sent the Syrian government more than $1 billion to help it withstand international sanctions. It has also shipped fuel to the country and sent two warships to a Syrian port in a display of power and support.

In March 2012, anonymous U.S. intelligence officials claimed a spike in Iranian-supplied arms and other aid for the Syrian government. Iranian security officials also allegedly traveled to Damascus to help deliver this assistance. A second senior U.S. official said members of Iran's main intelligence service, the Ministry of Intelligence and Security, were assisting Syrian counterparts in charge of the crackdown.

According to a U.N. panel in May 2012, Iran supplied the Syrian government with arms during the previous year despite a ban on weapons exports by the Islamic Republic. Turkish authorities captured crates and a truck in February 2012, including assault rifles, machine guns, explosives, detonators, 60 mm and 120 mm mortar shells as well as other items on its border. It was believed these were destined for the Syrian government. The confidential report leaked just hours after an article appeared in The Washington Post revealing how Syrian opposition fighters started to receive more, and better, weapons in an effort paid for by Persian Gulf Arab states and co-ordinated partly by the US. The report investigated three large illegal shipments of Iranian weapons over the past year and stated "Iran has continued to defy the international community through illegal arms shipments. Two of these cases involved [Syria], as were the majority of cases inspected by the Panel during its previous mandate, underscoring that Syria continues to be the central party to illicit Iranian arms transfers." More anonymous sources were cited by the UN in May 2012, as it claimed arms were moving both ways between Lebanon and Syria, and alleged weapons brought in from Lebanon were being used to arm the opposition. The alleged spike in Iranian arms was likely a response to a looming influx of weapons and ammunition to the rebels from Gulf states that had been reported shortly before.

On 24 July 2012, Islamic Revolutionary Guards Corp commander Massoud Jazayeri said Iranians would not allow enemy plans to change Syria's political system to succeed.

In August 2012, Leon Panetta accused Iran of setting up a pro-Government militia to fight in Syria, and chairman of the joint chiefs of staff General Martin Dempsey compared it to the Mahdi Army of Iraqi Shia leader Muqtada al-Sadr. Panetta said that there was evidence that the Iranian Revolutionary Guards were attempting to "train a militia within Syria to be able to fight on behalf of the regime". 48 Iranians were captured by the FSA in Damascus, and U.S. officials said that the men who were captured were "active-duty Iranian Revolutionary Guard members".

In September 2012, Western intelligence officials stated that Iran had sent 150 senior members of the Iranian Revolutionary Guards to preserve the Assad government, and had also sent hundreds of tons of military equipment (among them guns, rockets, and shells) to the Assad government via an air corridor that Syria and Iran jointly established. These officials believed that the intensification of Iranian support had led to increased effectiveness against the Free Syrian Army by the Assad government.

According to rebel soldiers speaking in October 2012, Iranian unmanned aerial vehicles had been used to guide Syrian military planes and gunners to bombard rebel positions. CNN reported that the UAV or drones—which the rebels refer to as "wizwayzi" were "easily visible from the ground and seen in video shot by rebel fighters".

Rebels have displayed captured aircraft they describe as Iranian-built drones — brightly colored, pilotless jets. They're accompanied by training manuals emblazoned with the image of Iran's revolutionary leader, the late Ayatollah Ruhollah Khomeini.Iranian drones guiding Syrian attacks, rebels say Nick Paton Walsh, CNN, October 31, 2012

2013 In January 2013, a prisoner swap took place between the Syrian Rebels and the Syrian Government authorities. According to reports, 48 Iranians were released by the Rebels in exchange for nearly 2,130 prisoners held by the Syrian Government. Rebels claimed the captives were linked to the IRGC.The Guardian, 9 January 2013, Assad regime frees more than 2,000 people believed to have opposition links in exchange for 48 detained Iranians US State Department spokeswoman Victoria Nuland described the Iranians as "members of the Iranian Revolutionary Guard," calling it "just another example of how Iran continues to provide guidance, expertise, personnel, technical capabilities to the Syrian regime."