Who they were
Reza Shah (1878–1944) was the commander of the Cossack Brigade who took power in the 1921 coup, became prime minister in 1923, and was crowned shah in 1925 after the Majlis deposed the Qajars, founding the Pahlavi dynasty. His rule was authoritarian: parliament was reduced to a rubber stamp, the press was controlled, and rivals were imprisoned or killed, while he amassed vast personal landholdings.
What they did
He drove a state-building program: a national army with conscription, a centralized bureaucracy, tribal settlement campaigns that were often brutal, the Trans-Iranian Railway (1927–38, financed by domestic taxes), the University of Tehran (1934), and secular courts and schools that curbed clerical institutions. He also reshaped society by decree, imposing Western dress codes and, in 1936, the forced unveiling of women (kashf-e hijab) — enforced by police and deeply divisive. In 1935 he asked foreign governments to use the name Iran instead of Persia.
Legacy
After his tilt toward Germany, Britain and the USSR invaded and occupied Iran in 1941 to secure the supply corridor, forcing him to abdicate in favor of his son Mohammad Reza; he died in exile in Johannesburg in 1944. The standard assessment holds two readings together: founder of the modern centralized Iranian state, and model of top-down, coercive modernization.