The Iranian Revolution of 1979 overthrows the Shah and establishes the world’s first modern Islamic republic under Ayatollah Ruhollah Khomeini. The ideological foundation is Khomeini’s doctrine of wilayat al-faqih (guardianship of the Islamic jurist) — the argument that during the occultation of the 12th Imam, a qualified Islamic scholar (faqih) should exercise political authority on the Imam’s behalf. This is a significant theological innovation: traditional Twelver Shia scholarship had generally held that full Islamic governance should await the return of the 12th Imam. The Islamic Republic is simultaneously a major experiment in political Shia theology and a significant regional power. Its tensions with Saudi Arabia represent the contemporary institutionalization of the Sunni-Shia divide. The Islamic Republic exports its Shia revolutionary ideology through Hezbollah in Lebanon, support for Hamas, and various other regional proxies.