In 1949 a Constituent Assembly was held in Iran to modify the Persian Constitution of 1906. Shah Mohammad Reza Pahlavi convened the assembly in April; he sought a royal prerogative giving him the right to dismiss the parliament, providing that new elections were held to form a new parliament. He also specified a method for future amendments to the Constitution. The amendments were made in May 1949 by unanimous vote of the Constituent Assembly.
During the previous year, the Shah had been considering changes to the Constitution as part of his various plans to increase the power of the monarchy. He was advised against this action by British and American diplomats who thought it unwise to unbalance the separation of powers. On 4 February 1949, an assassin shot at the Shah, two bullets wounding him. That evening, the government declared martial law and a special session of parliament imposed harsh measures against the Shah's political enemies. The assassin was suspected of being connected to the religious fundamentalist group Fada'iyan-e Islam (Martyrs for Islam, or Devotees of Islam), and loosely associated with the communist-leaning Tudeh Party of Iran. The parliament outlawed the Tudeh Party and had its leaders arrested. The Shah sent pragmatic Ayatollah Abol-Ghasem Kashani to exile—he had formed a strategic alliance with the Fada'iyan. In an atmosphere of national sympathy for the monarchy, the Shah called for a constituent assembly to make amendments to the Constitution, to give him more power. He selected the constituent assembly members from his supporters. He also increased his pressure for the formation of the Senate of Iran, an upper house of parliament that had been written into the constitution in 1906 but never formed. The Senate was expected to favor the Shah.