Iraq is the focal point of a strategic competition between Iran and the United States. Ever since U.S. forces invaded Iraq in 2003, Iran has relentlessly sought to impose its will on the country and expand its power in the region. Although not entirely successful, it has gained strategic depth in Iraq and has been able to use the support it garners from Iraqi Shias and Kurds to disrupt those U.S. operations that run counter to its agenda. And when U.S. and Iranian interests overlap, the Islamic Republic has been able to support the United States in ways that enhance its own power. The apparent contradiction in Iran's activities makes Iran what I call a "spoiler power" in Iraq; it is insufficiently powerful to impose its own agenda on Iraq but influential enough to disrupt U.S. operations through asymmetrical means. Over time, Iran's behavior as a spoiler power has also undermined the United States' ability to contain it.
The Bush administration's thunderous march to Baghdad in 2003 shocked and awed all the way to Tehran. Feeling encircled by the U.S. troops operating across its eastern border in Afghanistan and then across its western border in Iraq, the Islamic Republic feared that it would be the next target. Yet by removing Saddam Hussein -- the person who had inflicted more destruction on Iran than anyone else in centuries -- the U.S. invasion also handed Tehran a priceless strategic gift: the opportunity to promote a friendly Shiite government in Saddam's stead. The Islamic Republic decided to respond to the situation with a three-pronged strategy: it sought to empower Shias in Iraq, make the occupation of Iraq as difficult and costly for the United States as possible without directly confronting U.S. troops, and develop a retaliatory capability inside Iraq to deter the United States from attacking Iran.
When the United States dissolved the Iraqi army soon after its invasion, moreover, it opened the door for Shias, including those who