The Ghaybah (Occultation) of Imam-e Zaman (the Imam of the Period) is the most important event in the political history of the Shi'ah creed that has practically divided shi'ah history in two separate periods, the period of the Imams' presence and the Occultation Period. The Major Occultation period began in 329 AH. A few days before his Major Occultation, in a letter to his fourth and last envoy, Ali ibn Muhammad Samuri, Imam Mahdi (A) announced that his Major Occultation period had arrived and that his second Coming would be dependent on God's will. the year 329 AH can be called the year of split in the history of the leadership. The occurrence of this event had major impacts on the Shi'ah history the most important of which is the vacuum of leadership. This event caused the division of the Shi'ah creed into several branches. The Shi'ah ulama (scholars) tried to formulate the theory of imamah (leadership) and restrict the number of the Imams to twelve individuals. They also tried to justify and explain the phenomenon of the Ghaybah after the ideological Attacks of the opposition. Their efforts in trying to resolve the problem of the Shi'ah leadership led to the creation of the theory of the "succession of scholars". They tried to demonstrate the theoretical and practical ways and means of how the Shi'ah should administer their lives inside the dominant Sunni society as well.
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