I read this quite some time ago, so any corrections you can add are welcome.

In 1947, Iran nationalized the oil industry. The American way of thinking at this time was that this “Communism” needed to stop.
A frightened Reza Pahlavi (the Shah) who had actually fled the country was brought back from Egypt to calm a worried nation from an Iranian Army coup deposing Prime Minister Mosaddegh.

This “coup” was conveniently arranged courtesy of two CIA agents, Kermit Roosevelt and Norman Schwarzkopf (I believe the father of Gen. Schwarzkopf of the first Gulf War notoriety).
The arrival of the Shah, apparently still in his pyjamas, was met with an adoring (staged) crowd and his subsequent rule speaks for itself.

There is much, much more to this story.