After his coronation in April 1926, Reza Shah continued the radical reforms he had embarked on while prime minister. He broke the power of the tribes, which had been a turbulent element in the nation, disarming and partly settling them. In 1928 he put an end to the one-sided agreements and treaties with foreign powers, abolishing all special privileges. He built the Trans-Iranian Railway and started branch lines toward the principal cities (1927–38).