1953 Iranian coup d'état

With discussions surrounding the potential return of Iran's Crown Prince, I've been reflecting on the deeper historical events that have shaped Iran's modern trajectory.

I understand that the United States and the United Kingdom played direct roles in the 1953 coup that removed Prime Minister Mohammad Mossadegh from power and restored Mohammad Reza Pahlavi as Shah. Backed strongly by the West, the Shah's regime ruled for decades and was known for its political repression, including the actions of SAVAK, his secret police.

In 1979, when the Shah was allowed into the U.S. for medical treatment, that decision appeared to be a major flashpoint that fueled revolutionary anger, ultimately contributing to the Islamic Revolution and the U.S. embassy hostage crisis.

I'm also aware that Zbigniew Brzezinski, who served as National Security Advisor under President Carter, underestimated the depth of revolutionary sentiment within Iran. His misjudgment represents a key failure in U.S. foreign policy at the time.

My questions:

1. What specific roles did the U.S. and U.K. play in the 1953 coup against Mossadegh?

2. How did the Shah's return to power reshape Iranian society and politics in the following decades?

3. How do historians assess the U.S. decision to admit the Shah in 1979 in terms of its impact on the Islamic Revolution?

4. How is Brzezinski's strategy and misreading of the situation evaluated in contemporary scholarship on U.S. foreign policy?

I appreciate any insights or recommended sources you may have. Thank you!

As far as I understand, most Gulf Arab countries have nationalised oil companies like Aramco etc. So why was it such a big deal that the Iranians would do the same. I understand there was also concern of Soviet access to the Gulf, but the real trigger was the nationalisation policies.