This paper is the first in a series by the Tony Blair Institute for Global Change looking at how the West has misunderstood the importance of the Iranian Revolution. Western policies on Iran—and on the Muslim world more broadly—have consistently overlooked the impact of the ideology born of the events of 1979. This means that the West has failed to understand how far Tehran is willing to go to export the revolution and spread the ideology. Without this understanding, Iran policy will remain ineffectual, and Western comprehension of the nature of the threat posed by many Iran-backed or -inspired Shia proxies in the region will remain inadequate.