A country of extreme strategic importance, Iran has undergone profound, often dramatic, changes. Its geo-political importance and rich resources have always made Iran a prime target for the covetous eyes of mighty world powers. With its unique geographical position, Iran has been the main center for superpower rivalries with its rulers seeking protection from one power against the other.It also aims at providing a comprehensive and objective consideration of the major contemporary issues, examining the factors which brought down a regime which was loyal to and an ally of the United States and the clerical-led movement which toppled the pro-Western Shah`s regime.