The Iranian-Syrian alliance stretches back over three decades, constituting one of the most enduring alliances among authoritarian regimes in the region. Officials of the Iranian regime have gone so far as to refer to Syria as "the 35th province [of Iran] and a strategic province for us." Syria has been so strategically central to Iran because it provides a crucial logistical “land bridge” to Hezbollah and access to Mediterranean ports, which is central to its regional ambitions.

Funeral in Tehran for a senior IRGC commander killed fighting in Syria in 2015.

Today, in a testament to this enduring partnership, Iran has come to play an integral role in sustaining the Syrian regime amidst the ongoing civil war, which began as a popular uprising in March 2011 as the "Arab Spring" swept the region. Iran is committed to supporting Assad because it cannot allow Hezbollah to be logistically cut off. The regime also wants to deny a victory to its regional Sunni rivals, and further consolidate its “Shia Crescent” stretching from the Persian Gulf to the Mediterranean through Iraq, Syria, and Lebanon.

In support of the Syrian regime's campaign of mass murder to suppress the popular unrest, Iran has conducted "an extensive, expensive, and integrated effort to keep President Bashar al-Assad in power as long as possible while setting conditions to retain its ability to use Syrian territory and assets to pursue its regional interests should Assad fall." Not only does Iran remain the country's "closest ally," declaring it will "support Syria to the end," but Iran increasingly plays the commanding role in the Syrian Civil War against the rebel forces. In August 2012, IRGC General Salar Abnoush declared, "Today [Iran is] involved in fighting every aspect of a war, a military one in Syria and a cultural one as well."

In 2012, Iran's military and economic support to the Syrian regime increased markedly in order to prevent the collapse of Assad's rule. This steadfast support has continued with the inauguration of new Iranian President Hassan Rouhani, a purported moderate. Speaking with Syrian Prime Minister Wael al-Halqi in August 2013, Rouhani vowed, "the Islamic Republic of Iran aims to strengthen its relations with Syria and will stand by it in facing all challenges. The deep, strategic and historic relations between the people of Syria and Iran… will not be shaken by any force in the world."

IRGC-Quds Force Commander Qassem Soleimani, who is said to be running the war in Syria, addressing Iran-backed fighters near Aleppo in 2015.

On the ground, Iran "[deploys] IRGC commanders to guide Syrian forces in battle strategy and Quds commanders to help with military intelligence." They are "backed up by thousands of Iranian paramilitary Basij volunteer fighters as well as Arabic speakers including Shi'ites from Iraq." In coordination with its patron Iran, Lebanese Hezbollah has become increasingly involved in the Syrian Civil War. Hezbollah has reportedly sent "thousands of fighters into Syria in coordination with the [Iranian Revolutionary] Guards." In addition to sending its own forces into battle, training Syrian troops, and supporting its Hezbollah proxies, Iran has begun "mobilizing thousands of fighters from Arab countries, primarily Lebanon and Iraq, to fortify Mr. Assad's security forces." In May 2013, The Wall Street Journal reported that "Iran has been recruiting thousands of Afghan refugees to fight in Syria, offering $500 a month and Iranian residency to help the Assad regime beat back rebel forces. Through its proxy strategy, Iran seeks to "guarantee that the mostly Alawite remnants of the Assad regime continue to provide support for Iranian activity in the Levant even if an opposition government takes power in Damascus."