The Rise of Reza Khan During a very short period, Reza Khan undermined the Iranian people’s religious values and endeavored to substitute them with western ones. He isolated Shiite clergies and diminished their influence for several years. Reza Khan omitted Shiite symbolic practices, such as the Ashura rituals, and replaced them with dancing, singing, and merrymaking carnivals. In February 21st, 1921, Reza Khan, the commander of Qazaq Division, made a coup d’etat. After a while he became the minister of war. In November 25th, 1923, Reza Khan was appointed as prime minister. In late 1925, he succeeded to the throne and was the Iranian monarch until September 1941. After the occupation of Iran by allied forces, Reza Khan was forced to resign and leave the country. 

The role of the British government in Reza Khan’s coup d’etat was so obvious that London never endeavored to deny it. Researchers who have investigated causes of the British inspired coup d’etat argue that Britain was, due to massive objections to the "1919 Agreement”, orchestrated this intrigue. "Adoption of the essence of the ‘1919 Agreement’ was the main objective of Reza Khan’s coup d’etat; in other words, this coup d’etat resulted in a kind of political stability in Iran which contributed to the protection of British Empire’s interests in the region.” After the coup d’etat of February 21st, 1921, Seyed Zia’eddin Tabatabaei assumed the post of premiership and Reza Khan was appointed as the minister of war. Seyed Zia’ government collapsed after 100 days. After the collapse of Seyed Zia’s cabinet, five more cabinets were formed in Iran. Two of these cabinets were established by Ahmad Ghawam; two others were formed by Moshirodouleh; and one cabinet was established by Mostoufiolmamalek. In all these cabinets, Reza Khan, who had been appointed as the minister of war at the end of Seyed Zia’eddin Tabatabaei’s cabinet, maintained this post. He played the greatest role in undermining the stability of these cabinets. In December 24th, 1923, Reza Khan assumed the post of premiership. He summarized his plans as prime minister in two phrases: 1. Preserving the rights of the nation; and 2. Implementation of the law. Quite ironically, Reza Khan violated the entire rights of the nation for his own advantage and trespassed all the laws in order to gain political power. 

Reza Khan considered Seyed Hassan Modarres as the most important challenge for consolidating the bases of his power. Therefore, he arrested and imprisoned Modarres immediately at the night of the coup d’etat. Modarres had realized the danger of Reza Khan’s dictatorship and resisted against him. Nevertheless, Reza Khan’s augmented political power and his influence over the Iranian press were great impediments for Modarres to develop his anti- Reza Khan initiatives. As a result, Reza Khan was moving towards the attainment of further political power, but Modarres was gradually weakened and isolated.