On February 21, 1921, Rezâ Khân, backed by the Cossack Brigade, staged a coup d’etat. He occupied Tehran, declared martial law, and installed a pro-British politician, Sayyid Ziâ-od-Din Tabâtabâi as prime minister. Rezâ Khân became commander of the army and minister of war. Tabâtabâi proved to be a disaster as prime minister. He made enemies on every side and alienated Rezâ Khân; he was forced to resign in May 1921 and fled the country. Rezâ Khân, on the other hand, proved to be a dynamic leader and the de facto ruler of the country. He expanded and reorganized the army, put down separatist revolts in the provinces, and brought in another American advisor to sort out the country’s finances. In 1923, Ahmad Shah named Rezâ Khân as prime minister and then promptly left for a European vacation, never to return. Inspired by the example of Mustafa Kemal in Turkey, there was increasing talk of making Iran a republic, with Rezâ Khân as president. Conservative and religious elements (perhaps prodded by Rezâ himself) objected to the idea of a republic as un-Islamic. In 1925, the Majles deposed Ahmad Shah and amended the constitution to transfer the monarchy to Rezâ Khân and his descendants; he crowned himself in a ceremony in 1926.

In accordance with a law regulating personal names, Rezâ Khân had adopted the family name of Pahlavi, and he was thus now Rezâ Shah of the Pahlavi Dynasty. The word itself was the name of a language of ancient Iran, and choosing it symbolized the Iranian nationalism that was the hallmark of Rezâ Shah’s policies. He was remarkably effective in breaking the power of the great tribal groups, in crushing any tendency toward provincial or ethnic separatism, and in building up the institutions of a centralized nation-state. He implemented many measures to instill a sense of pride and unity and national identity, ranging from encouraging the study of Iranian antiquities to regulating the kind of clothes people could wear to demanding that foreigners call the country Iran instead of Persia. In addition to nationalist policies, Rezâ Shah leaned toward the secularization of society, particularly after his visit with Mustafa Kemal Ataturk in 1934. Of his various reforms, the introduction of civil law and courts, the state control of education, and the emancipation of women struck most clearly at the traditional role of religion in Iranian society. Although he never pushed as hard in any of these areas as Ataturk had done in Turkey, the changes were enough to earn him the animosity of many religious leaders. They were too overawed by him, however, to make much trouble; as he is supposed to have said, it was easy to control the clergy simply by bribing the corrupt and beating the rest.

In foreign policy, Rezâ Shah dealt firmly if cautiously in his relations with the Soviet Union and Great Britain. Iranians tend to believe that Britain organized the coup which brought Rezâ Khân to power and that Rezâ Shah was essentially a British puppet; nonetheless, he was quite bold in taking action at British expense. In defiance of British demands, he had suppressed the efforts of the Arab Shaykh Khaz‘al to gain autonomy in Khuzestân in 1924; in 1932 he cancelled the British oil concession and forced a renegotiation of its terms under the auspices of the League of Nations; in 1940, taking advantage of wartime conditions, he extracted higher royalty payments from the Anglo-Iranian Oil Company (the name of the company had been changed in accordance with Rezâ Shah’s insistence on the use of the name Iran rather than Persia for his country). Rezâ Shah also succeeded in improving and strengthening Iran’s ties with its regional neighbors, and he continued the Iranian policy of seeking close relations with a third Western power to offset the influence of the Russians and the British. For a number of reasons, economic and cultural, that power turned out to be Nazi Germany. After Hitler invaded the Soviet Union in 1941, the USSR joined Britain in claiming that the rise of German influence in Iran was intolerable; this was mostly a pretext for aggression since the Allies needed control of Iran to facilitate their defense against the German advance and to secure the unimpeded movement of lend-lease equipment from the Persian Gulf to the Soviet Union. In August 1941, the Soviets invaded Iran from the north, and the British attacked by sea in the Persian Gulf. Iranian resistance collapsed after three days; a few weeks later, Rezâ Shah abdicated in the hope of preserving the throne for his son Mohammad-Rezâ Pahlavi. Since the Allies could not find anyone else they could agree on as a successor, they accepted this arrangement. Rezâ Shah died in exile in 1944.

By the terms of the Tripartite Treaty (1942) and the Tehran Declaration (1943), the Allies were obligated to maintain the sovereignty and territorial integrity of Iran, to withdraw their forces after the war, and to contribute to the economic reconstruction of the country. The Soviets, however, built up the Communist (Tudeh) Party in Iran, backed separatist movements among the Kurds and in Azerbaijan, and actually increased the number of their troops in Iran. The United States was a signatory to the Tehran Declaration and thus a party to its commitments; its efforts to bring about the withdrawal of Soviet forces from Iran constituted an opening round in the Cold War and marked the beginning of America’s protracted, convoluted, and ultimately disastrous involvement in Iranian affairs.

In 1949, a group of liberal, nationalistic Iranians led by Mohammad Mosaddeq, a politician renowned for his honesty and integrity, formed an organization called the National Front and began to agitate for terminating the agreement with the Anglo-Iranian Oil Company and nationalizing the company. A bill to that effect was passed in 1951, and the Majles asked Mohammad-Rezâ Shah to appoint Mosaddeq as the prime minister to implement the measure. This enraged the British government, which used any number of means to try to prevent or overturn the nationalization. After military threats, legal actions, and a boycott of Iranian oil, the British succeeded in winning the support of the Eisenhower administration for a covert operation to overthrow Mosaddeq. This conspiracy was facilitated by the internal conditions in Iran, where Mosaddeq faced economic problems caused by the loss of oil revenue and growing political divisions. Already at odds with royalists because of his perceived hostility toward the monarchy, he was also caught between the conflicting interests of the Communists and the conservative religious groups—they supported Mosaddeq on the nationalization of oil but were naturally at odds with each other on everything else. The foreign intelligence agents in Iran, directed by a CIA operative, did everything possible to split the religious elements from Mosaddeq and align them with the royalists, even sending out agents disguised as Communists to threaten religious leaders and stir up violent demonstrations. One of their hardest tasks proved to be convincing the shah to collaborate in the plot; he was finally persuaded in August 1953 to exercise his authority to dismiss Mosaddeq as prime minister. When Mosaddeq refused to accept the dismissal, the shah fled the country and crowds of demonstrators clamored for the abolition of the monarchy. They were sometimes incited to violence, it seems, by agents provocateurs in order to alarm the conservatives and arouse fears of a Communist takeover. A few days later, a massive pro-royalist demonstration, organized and funded by the conspirators, rushed through Tehran; units of the army surrounded Mosaddeq in his house and arrested him when he tried to escape. Mohammad-Rezâ Shah then returned in triumph to Iran.

From 1953 onward, political life in Iran was increasingly and, before long, thoroughly controlled by the shah himself, who almost always adopted policies attuned to expectations of what would be most pleasing to the presidential administrations in Washington. In the 1960s, the Kennedy era, he was concerned to show himself as a progressive and enlightened ruler. His so-called Revolution of the Shah and the People, also known as the White Revolution, promised land reform, economic reform, improvements in education, programs for health care and increased rates of literacy (especially in rural areas), and voting rights for women. It delivered somewhat less than all that but was still radical enough in its effects to alienate religious leaders and arouse protest demonstrations, which were violently suppressed in 1963 and 1964. One of the chief instigators of this opposition was an âyatollâh (a high-ranking member of the clergy), Ruhollâh Khomeini, who was briefly imprisoned and finally sent into exile. In the 1970s, the Nixon era, the shah sought to portray himself as a strong and reliable regional ally capable of maintaining order and stability in the Persian Gulf area. Through OPEC, he was able to lead the drive to raise oil prices, and then, with his vastly increased revenues, he was able to purchase an impressive arsenal of advanced military hardware from the United States and elsewhere. Economically, too, he claimed that he was building a great civilization (tamaddon-e bozorg ) and that Iran would take its place as an advanced industrial nation alongside countries like Germany or Japan. He also became even more ruthlessly autocratic and insensitive to the country’s cultural values, crushing any political dissent and on at least one occasion openly mocking the abilities of his people. He could be both megalomaniacal and contemptuous of Islamic religious concerns, exalting the country’s pre-Islamic history, holding an opulent celebration at Persepolis of 2500 years of monarchy in Iran, introducing a new imperial calendar in place of the Islamic calendar, and enacting laws that contradicted Islamic teachings.