The Islamic Republic of Iran is a key patron of the Lebanese Shia Islamist militia and political party Hezbollah.
Iranian support, including financial aid, deployment of Revolutionary Guards, and training, has played an important role in Hezbollah's formation and development. Hezbollah has functioned as Iran's proxy since its inception, and is considered to be part of the "Axis of Resistance".
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.