Once installed as prime minister, Bakhtiar took several measures designed to appeal to elements in the opposition movement. He lifted restrictions on the press; the newspapers, on strike since November, resumed publication. He set free remaining political prisoners and promised the dissolution of SAVAK, the lifting of martial law, and free elections. He announced Iran's withdrawal from CENTO, canceled US$7 billion worth of arms orders from the United States, and announced Iran would no longer sell oil to South Africa or Israel. Although Bakhtiar won the qualified support of moderate clerics like Shariatmadari, his measures did not win him the support of Khomeini and the main opposition elements, who were now committed to the overthrow of the monarchy and the establishment of a new political order. The National Front, with which Bakhtiar had been associated for nearly thirty years, expelled him from the movement. Khomeini declared Bakhtiar's government illegal. Bazargan, in Khomeini's name, persuaded the oil workers to pump enough oil to ease domestic hardship, however, and some normalcy returned to the bazaar in the wake of Bakhtiar's appointment. But strikes in both the public and the private sector and large-scale demonstrations against the government continued. When, on January 29, 1979, Khomeini called for a street "referendum" on the monarchy and the Bakhtiar government, there was a massive turnout.

Bakhtiar sought unsuccessfully to persuade Khomeini to postpone his return to Iran until conditions in the country were normalized. Khomeini refused to receive a member of the regency council Bakhtiar sent as an emissary to Paris and after some hesitation rejected Bakhtiar's offer to come to Paris personally for consultations. Bakhtiar's attempt to prevent Khomeini's imminent return by closing the Mehrabad Airport at Tehran on January 26, 1979, proved to be only a stopgap measure.

Khomeini arrived in Tehran from Paris on February 1, 1979, received a rapturous welcome from millions of Iranians, and announced he would "smash in the mouth of the Bakhtiar government." He labeled the government illegal and called for the strikes and demonstrations to continue. A girls' secondary school at which Khomeini established his headquarters in Tehran became the center of opposition activity. A multitude of decisions, and the coordination of the opposition movement, were handled here by what came to be known as the komiteh-ye Imam, or the Imam's committee. On February 5, Khomeini named Mehdi Bazargan as prime minister of a provisional government. Although Bazargan did not immediately announce a cabinet, the move reinforced the conditions of dual authority that increasingly came to characterize the closing days of the Pahlavi monarchy. In many large urban centers local komitehs (revolutionary committees) had assumed responsibility for municipal functions, including neighborhood security and the distribution of such basic necessities as fuel oil. Government ministries and such services as the customs and the posts remained largely paralyzed. Bakhtiar's cabinet ministers proved unable to assert their authority or, in many instances, even to enter their offices. The loyalty of the armed forces was being seriously eroded by months of confrontation with the people on the streets. There were instances of troops who refused to fire on the crowds, and desertions were rising. In late January, air force technicians at the Khatami Air Base in Esfahan became involved in a confrontation with their officers. In his statements, Khomeini had attempted to win the army rank and file over to the side of the opposition. Following Khomeini's arrival in Tehran, clandestine contacts took place between Khomeini's representatives and a number of military commanders. These contacts were encouraged by United States ambassador William Sullivan, who had no confidence in the Bakhtiar government, thought the triumph of the Khomeini forces inevitable, and believed future stability in Iran could be assured only if an accommodation could be reached between the armed forces and the Khomeini camp. Contacts between the military chiefs and the Khomeini camp were also being encouraged by United States general Robert E. Huyser, who had arrived in Tehran on January 4, 1979, as President Carter's special emissary. Huyser's assignment was to keep the Iranian army intact, to encourage the military to maintain support for the Bakhtiar government, and to prepare the army for a takeover, should that become necessary. Huyser began a round of almost daily meetings with the service chiefs of the army, navy, and air force, plus heads of the National Police and the Gendarmerie who were sometimes joined by the chief of SAVAK. He dissuaded those so inclined from attempting a coup immediately upon Khomeini's return to Iran, but he failed to get the commanders to take any other concerted action. He left Iran on February 3, before the final confrontation between the army and the revolutionary forces.

On February 8, uniformed airmen appeared at Khomeini's home and publicly pledged their allegiance to him. On February 9, air force technicians at the Doshan Tappeh Air Base outside Tehran mutinied. Units of the Imperial Guard failed to put down the insurrection. The next day, the arsenal was opened, and weapons were distributed to crowds outside the air base. The government announced a curfew beginning in the afternoon, but the curfew was universally ignored. Over the next twenty-four hours, revolutionaries seized police barracks, prisons, and buildings. On February 11, twenty-two senior military commanders met and announced that the armed forces would observe neutrality in the confrontation between the government and the people. The army's withdrawal from the streets was tantamount to a withdrawal of support for the Bakhtiar government and acted as a trigger for a general uprising. By late afternoon on February 12, Bakhtiar was in hiding, and key points throughout the capital were in rebel hands. The Pahlavi monarchy had collapsed.

Data as of December 1987