Rezā Shāh Pahlavi (reˈzɑː ˈʃɑːhe pæhlæˈviː, born Rezā Khan (March 15, 1878 – July 26, 1944), was the Shah of the Imperial State of Iran from December 15, 1925, until he was forced to abdicate by the Anglo-Soviet invasion of Iran on September 16, 1941.
In 1925, Reza Shah overthrew Ahmad Shah Qajar, the last Shah of the Qajar dynasty, and founded the Pahlavi dynasty. He established a system of government that revitalized the goals of the Constitutional Revolution of Iran where for the first time Iranians were seeking for rulers who do not remain in power for eternity. Known for being quite intelligent despite his lack of formal and academic education, Reza Shah introduced many socio-economic reforms, reorganizing the army, government administration and finances. To his supporters his reign brought “law and order, discipline, central authority, and modern amenities — schools, trains, buses, radios, cinemas, and telephones”.
However, his attempts at modernisation have been criticised for being “too fast”(wikipedia) (لینک با توضیحات فارسی)