Realism posits that alliances are instrumental in achieving balances of power in international relations, irrespective of ideological or domestic differences between states. Realists argue that nations, regardless of their internal governance structures, come together to counter mutual threats and emphasize pragmatic concerns over ideological affinities. A classic example is the unlikely alliance between the US and the Soviet Union against Nazi Germany during the Second World War.

Contrary to popular narratives that frame Iran's support for Syria as sectarian, I argue that Tehran's backing of Damascus is driven by realist considerations. Since 2013, Iran has extended substantial support to the Syria regime, which has undoubtedly helped it survive. The timing and scale of Iran's intervention – which has come in the form of military, personnel, arms, energy and financial aid – arrived at a time when the regime was under severe pressure from opposition forces and looked in danger of losing “useful Syria”, which is aligned with Tehran's interests that seek to secure the corridor linking Syria's coastal region to Lebanon (Ghaddar 2016). Iran has supported Syria to secure its own strategic interests in the region and has not done so out of love for Asad. The fall of the Asad regime threatened to weaken Iran's regional influence by undermining its management of the axis of resistance.

While Russian intervention has focused on supporting state structures and institutions, Iran has built up non-state actor capabilities, including semi-autonomous armed groups, new charitable organizations and independent business associations (Saban 2020). The purpose of building non-state actor capabilities, which has served its interests well in Iraq, is to create enduring networks of interest that can outlast the Syrian regime, should it fall at some point (Fulton, Holliday & Wyer 2013). In other words, Iran has not only propped up the Asad regime but also invested in a policy that secures Tehran's interest in the event the regime falls. It is the ultimate realist policy.

This chapter provides a brief history of Syrian–Iranian relations and traces how the partnership has evolved over the last 50 years. Having set the context, it then considers the reasons behind Iran's decision to support Syria – wholeheartedly – and highlights the scale of its military and financial assistance, which undoubtedly has allowed the regime to survive.