The CIA was responsible, under Eisenhower's direction, for overthrowing Mosaddegh in Iran, leading to the Shah, and then the hostage crisis and the current regime. When you wave your hands and pretend to be adding up wins and losses like this, do you consider where the CIA is a net liability? How did their arming of the Afghans who would later become the Taliban work out, in your accounting?
I have to disagree with the word "responsible". There was a huge domestic opposition to Mosaddegh's rule in Iran. Did the CIA encourage this dissent? Yes. Did the CIA hasten the overthrow of Mosaddegh? Yes.
If the CIA had never gotten involved in Iran, would Mosaddegh have maintained rule? It's doubtful.
The CIA, in its own words, seems to feel that it was responsible for the "overthrow" of Mosaddegh, in a "coup" (their words).
At the time of the coup, Mosaddegh was more popular than before, enjoying majority support, and had just been granted emergency powers by parliament for six months, which then renewed them for twelve. I respectfully dispute your suggestion that, absent CIA interference, it's doubtful that he would have maintained rule.
1. The plot to overthrow Mosaddegh went off exactly as planned. Ignoring any moral factors, it was very a impressive operation. I wouldn't doubt that CIA took as much responsibility for it as they could.
2. It is true that Mosaddegh had broad popular support, but he was also opposed by a large fraction of the population (eg. the mass protests that called for his head).
I'll take back the comment that he wouldn't have been able to maintain rule (I'll readily admit I can't predict the future). However, my point is that the CIA didn't create a coup out of thin air.
What the CIA did in Iran was provide operational support for the anti-Mosaddegh forces. Not really all that different than what the CIA did in Afghanistan during the war with Russia.
Mosaddegh wanted to nationalize oil, are you telling us that BP (then APOC), the UK, the US were all happy about it and the Iranian public was furious to see the oil money coming back to their country?
What about the coups and assassinations in several dozen other countries? Chile 9/11/1973, Brazil 1964, Guatemala 1954, Venezuela 1992+2002, Haiti 1991+2004 (Aristide was forced to board a US military plane that took him into exile), Congo coup 1960 and Patrice Lumumba's assassination 1961?
