The constitutional revolution of 1905 is seen to result from the impact of Western political values on Iran's traditional society. Reza Shah's dictatorship is explained in the context of compromise between feudalism and growing capitalism. The roles and interactions of nationalism, religion, communism and political parties in Iran, particularly during 1945-1953, shows they were the reflection of profound changes within society. The Shah's policies were politically motivated; they caused social dislocation and the politicization of the peasantry. The regime's failure to respond to these forces brought about its isolation. We confirm Huntington's concept of political development and decay. Iran's changes of discontinuity and violence are seen clearly. This study recommends the strengthening of the political channels of communication for Iran.