This book deals with the Great Power Rivalry in Iran throughout the period 1921 to 1979 and the Iranian foreign policy coping with this situation. It makes a preliminary attempt to generalize the factors of this rivalry and examines three basic parameters necessary for its outbreak: the inequality of the states at the international level, the power vacuum inside Iran, and the rivals' vital interests of oil and the strategic corridor in Iran. Exploring the Iranian foreign policy formulation in both eras of the Pahlavi kingdom, the book argues that the Shah, on top of the small oligarchy, was the actual key decision-maker and the pervasive opposition of the Iranian people, including autonomous revolts, communists, religious and democratic movements, and the Shah's suppression of them all, made the state unstable and hence vulnerable to foreign pressures. Due to these failures, the book concludes that Iran's foreign policy in order to secure its oil resources and territorial integrity was always in alignment with the West against the Soviet Union rather being independent toward the two.