Two good references: 1. All Fall Down, by G. Sick, I.B. Tavris Publishers, 1985; 2. Mission to Tehran, by R.E. Huyser, Deutsch publishing, 1986.
Americans (with the help of the British) have been credited (or blamed) for bringing Shah back into power, in 1953. They also certainly had a dominant determining influence over the Shah’s regime from that point until early 1970’s. During the 1950’s, almost half of Iran’s budget and most of the army equipment were supplied through the American aid programs, as a way to prevent a collapse into the Soviet sphere. With the rising oil revenues in the 1960’s, Iran became less and less dependant on that aid, and Shah turned from a timid US puppet, to a credible ally. The turning point came in 1971, when the Iran-Saudi axis was established to fill the military vacuum left by the departing British forces, in the Persian Gulf.
The 1973 oil crisis propelled Shah into the world arena, as a very ambitious and exceedingly powerful leader. The power-balance pendulum worked so much to Shah’s advantage that in 1974, it was him paying cash to influence the outcome of the US presidential elections. Therefore, at the start of revolution, Shah was not an American puppet; and he was even on occasion standing up to them, and unduly interfering with their internal politics! This made the then new democrat president (Jimmy Carter) suspicious of the Shah. Carter initially weighed on the Shah to lower his military ambitions, respect human rights against political prisoners, and create a more “open political atmosphere”. However, at the first signs of troubles in 1977, Carter abandoned all his reform-minded agenda, as he realized that Iran was not a country that US could afford to lose.
In early 1978, the direct US influence in Iran was minimal. Shah was completely in control, and would not even let the US intelligence agencies perform an independent evaluation and form an unbiased view of the internal political situation in Iran. Therefore, the misinformed US operatives in Iran did not take the opposition demonstrations seriously; as for example, their ambassador took the whole summer off! It was only during the massive student demonstrations in the fall of 1978 that the US embassy woke up to the depth and breadth of the Islamic outbreak. That rude awakening is evident in the ambassador’s famous “thinking the unthinkable” memo to the president. There, he suggested that the opposition action and strength had reached a critical-mass and could not be resisted by the Shah, even with full American support! The recommendation was to immediately open a channel of dialogue with the opposition leadership and plan for a working relationship with them, as they would be transitioning to power!
That memo almost cost the ambassador his job, as the president became furious at what he saw as a timid abandoning of a strategic ally. Problem was that Carter was not in Tehran to see things first hand, and know how everything had gone topsy-turvy, since his visit 10 months ago. Hence, the president directed his ambassador to forget about any talk with the opposition, and shore up as much support for the Shah as possible. Shah in turn was, by then, so depressed and afraid of the revolution that he asked for direct guidance from the Americans. That’s when the Carter administration prepared the famous “options letter” for the Shah. There, instead of a clear direction, they outlined four alternative and divergent courses of action for the beleaguered monarch, ranging from a de-facto abdication to a bloody military coup. The Shah’s reply showed his true personality weakness.
In times of hardship, everyone shows their true colors, and Shah’s came out yellow; perhaps due to the tormenting cancer, perhaps due to the corrupting effect of 15 years of absolute power. He begged the Americans to give him one clear direction, and not a bunch of options. Carter’s reply was that his majesty was the Shah of Iran and whichever of those options that he chose, US would fully support him! At that point, all first hand accounts point to the fact that Shah had completely turned paranoid and at the verge of a nervous breakdown. In his afflicted mind, the Americans and the British were taking revenge on him (for jacking up the oil prices) and wanted to get rid of him; as they had got rid of his father, when he had become disobedient. Shah decided to go with what he thought as the American will, i.e. relinquishing power to a moderate prime minister and leaving for an extended vacation.
As a back-up plan, the Shah and Americans agreed to prepare for a bloody coup that in case of the probable collapse of the Bakhtiar government; the military generals could step in and take over the government and brutally suppress the opposition. However, when an American general in charge of the operations came to Iran, he noticed that Shah had warned all the Iranian generals against cooperating with him. He also found that there was no coherent and cooperative command structure to the Iranian general staff, and every general was getting his direct commands from the Shah himself; often during one-on-one meetings and in total isolation from the other commanders! The only thing that the frightened Iranian generals kept repeating to the American agent was that, “do not allow Shah to leave; without him we will fall in a week!” Since the 1960’s, Shah had been so suspicious of a military coup that over the years, he had tied all the army generals, and decision making processes, directly to himself. Without him, the command structure collapsed like a house of cards.
Immediately after the revolution, the Americans severed all formal ties to the Pahlavi family and soon treated Mohammad Reza as persona-non-grata. Their mission in Tehran quickly recognized the new Islamic Republic and started to establish a working relationship with both the moderate and the Islamist fractions inside the government. That was, until a group of rightwing republicans petitioned the Carter administration for six months, to get a medical visa for the ailing ex-Shah. The rest is history.