Iran and Syria have enjoyed one of the most enduring alliances in the Middle East, with the relationship surviving the Iran—Iraq war, decades of international sanctions, and the Iranian nuclear dispute. The alliance took on new significance after the outbreak of war in Syria in 2011 when Iran, led by President Mahmoud Ahmadinejad, provided decisive diplomatic and materiel support for the Syrian regime. The largesse of this support suggested that for many in Tehran, the Iran—Syria alliance remained as important in 2011 as it was when it was established in 1979. The election of the reformist President Hassan Rouhani in 2013 appeared to complicate this calculus, with speculation emerging that he would temper Iran’s support for Syria. In practice, however, Rouhani’s response to Syria has been muted, reflecting an attempt to placate the international community while simultaneously preserving Iran’s most reliable regional alliance. In doing this, Rouhani has also inadvertently revealed the deeply polarizing impact that the Syrian crisis has had on the Iranian political elite, as well as the limits of presidential power in Iran.