As a result of this maneuvering, Iran achieved two goals. First, the Americans disposed of Iran's archenemy, Saddam Hussein, turning Iraq into a strategic cripple. Second, Iran helped force the United States out of Iraq, creating a vacuum in Iraq and undermining U.S. credibility in the region -- and sapping any U.S. appetite for further military adventures in the Middle East. I want to emphasize that all of this was not an Iranian plot: Many other factors contributed to this sequence of events. At the same time, Iranian maneuvering was no minor factor in the process; Iran skillfully exploited events that it helped shape.
There was a defensive point to this. Iran had seen the United States invade the countries surrounding it, Iraq to its west and Afghanistan to its east. It viewed the United States as extremely powerful and unpredictable to the point of irrationality, though also able to be manipulated. Tehran therefore could not dismiss the possibility that the United States would choose war with Iran. Expelling the United States from Iraq, however, limited American military options in the region.
This strategy also had an offensive dimension. The U.S. withdrawal from Iraq positioned Iran to fill the vacuum. Critically, the geopolitics of the region had created an opening for Iran probably for the first time in centuries. First, the collapse of the Soviet Union released pressure from the north. Coming on top of the Ottoman collapse after World War I, Iran now no longer faced a regional power that could challenge it. Second, with the drawdown of U.S. forces in the Persian Gulf and Afghanistan, the global power had limited military options and even more limited political options for acting against Iran.
Iran now had the opportunity to consider emerging as a regional power rather than solely pursuing complex maneuvers to protect Iranian autonomy and the regime. The Iranians understood that the moods of global powers shifted unpredictably, the United States more than most. Therefore it knew that the more aggressive it became, the more the United States may militarily commit itself to containing Iran. At the same time, the United States might do so even without Iranian action. Accordingly, Iran searched for a strategy that might solidify its regional influence while not triggering U.S. retaliation.