Iranian intervention in the Syrian civil war

The Islamic Republic of Iran and the Syrian Arab Republic are close strategic allies, and Iran has provided significant support for the Syrian government in the Syrian civil war, including logistical, technical and financial support, as well as training and some combat troops. Iran sees the survival of the Syrian government 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 began sending tens of thousands of volunteers in co-ordination with the Syrian government to prevent the collapse of the Syrian Arab Army; thereby polarising the conflict along sectarian lines.

Iranian security and intelligence services are advising and assisting the Syrian military in order to preserve Bashar al-Assad's hold on power. Those efforts include training, technical support, and combat troops. Estimates of the number of Iranian personnel in Syria range from hundreds to tens of thousands. Lebanese Hezbollah fighters, backed by Iran's government, have taken direct combat roles since 2012. 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 Syrian President Assad. Estimates of financial assistance range from tens to hundreds of billions of dollars. Iran has portrayed its intervention as part of a religious and historical revanchist mission to subordinate Sunnis and seek vengeance. Tehran's objectives include attempts to Shi'ification 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 are supported by ballistic missile 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 had been deployed to Syria. As of 2018, 2000 officers of the Quds Forces command an estimated 131 military garrisons and tens of thousands of Iran-backed Shia jihadists across regime-controlled regions. As of 2023, Iran maintains 55 military bases in Syria and 515 other military points, the majority in Aleppo and Deir Ezzor governorates and the Damascus suburbs; these are 70% of the foreign military sites in the country.