Fifty years ago today, the CIA helped overthrow Mossadegh in Iran, installing the Shah in his place, setting into motion a chain of events which would eventually lead to the revolution in 1979 and the rise of militant Islamic fundamentalism in the region and therefore arguably, at least in part, to the events of September 11, 2001.
It’s called the Law of Unintended Consequences, and as any small town sherriff will be happy to tell you, ignorance of the law is no excuse.
(A good book on the subject is All the Shah’s Men by Stephen Kinzer.)