Then they used their front man Imad Mugniyeh to attack our embassy in Lebanon, then they killed hundreds of French and US military men in their barracks. Then they abducted assorted US citizens and westerners and held them hostage. Then they nabbed our CIA station chief and slowly tortured him to death.
Then they attempted to sink US flagged ships in the Persian Gulf.
In flailing around looking for a way to overcome iraq in the Iran Iraq war they decided to use thousands of Iranian children - to whom they had given plastic keys, telling them they were "keys to heaven" as they tied the kids up in ranks and used them in suicide waves to swarm Iraqi positions because the religious nuts safely sipping tea in Qom and their former pals the communist students had already tortured and murdered so many of the Shah's trained military personnel that children were about the only thing they had left to throw at the enemy.
Then they tried to use speedboats Tamil-Tiger style against US warships, which did not go well for them. Then they attempted to take out a US ship with an airliner.
Then they murdered a bunch of US personnel at Khobar Towers.
Then they and their Hezbollah pals moved into South America to spawn terrorism against US and Israeli interests there.
Then they worked with al Qaeda on blowing up the USS Cole after the attempt to sink the USS The Sullivans failed, and so on.
Then Iran got involved in the Balkans and magically the Egyptian terrorists who had fled there were armed and trained. They reappeared later as the 1993 World Trade Center bombers and the Luxor massacre perps led by the Blind Sheikh.
Then they provided safe passage to Iraq for Zarqawi's al Jihad al Tawhid /Ansar al Islam forces as they fled Afghanistan... the group which later became "al Qaeda in Iraq," a group which incidentally was in more recent times involved in the attack on the US in Benghazi and is now entrenched in Syria.
Apparently they're holding a US citizen at the moment, maybe more than one. And for a while now, Iran's buddy Zawahiri the Egyptian has been free to operate al Qaeda without the annoying spawn of a Yemeni, OBL, in the way, and Zawahiri is a good deal more cunning.
Like Churchill said about Russia, the key to understanding Iranian behavior is national interest. When in conflict, national interest and national survival trump ideology. Iran has not survived for fifteen hundred years by risking national survival for the benefit of Sunnis.