An officer of the Persian Cossack Brigade, he achieved power through an army coup (1921) and established a military dictatorship. He was successively Minister of War and Prime Minister before becoming Shah. He followed a policy of rapid modernization, constructing a national army, a modernized administrative system, new legal and educational systems, and economic development, notably through the Trans-Iranian Railway (1927–38). He crushed tribal and other opposition to his policies. In World War II his refusal to expel German nationals led to the invasion and occupation of Iran by Soviet and British forces. He was forced to abdicate in favour of his son, Muhammad Reza Shah Pahlavi, and died in exile in South Africa.