Iranian intervention in the Syrian civil war

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. 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. 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. Estimates of the number of Iranian personnel in Syria ranged from hundreds to tens of thousands. Lebanese Hezbollah fighters, backed by Iran's government, 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. 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. 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.