The alliance between Syria and Iran has proved to be an enduring feature on the political landscape of the Middle East. Moreover, since its inception after the Iranian Revolution, it has had a significant impact in terms of moulding events and bringing about major changes in this troubled region. The study demonstrates that, contrary to prevailing views, the alliance between the two states has been essentially defensive in nature. It emerged in response to a series of events and developments, most notably, the Iraqi invasion of Iran in 1980, the Israeli invasion of Lebanon in 1982 and US adventurism in the Middle East. The book traces the critical stages in the evolution and consolidation of the alliance in the 1980s, and offers explanations for its longevity into the 21st century.