An American military campaign against Iran would only succeed at great cost. The Iranian military is better organized and equipped than many countries in the region. Through the use of intermediate range missiles, Iranian forces could effectively engage large U.S. installations in Iraq, Kuwait, Afghanistan, Qatar, and Bahrain, as well as U.S. Arab allies in the Persian Gulf. U.S. naval vessels could be highly vulnerable to Iranian modern anti-ship missiles as well.
After the United States suppresses Iran’s integrated air defense systems and anti-aircraft fire, U.S. forces should be capable of destroying the regime in Tehran, at least in the short term. However, the prospect of occupying and stabilizing a country whose population and landmass far exceed that of Iraq should be a formidable deterrent. If, after initial costs of $2 trillion and decades of U.S. involvement, Iraq is still in disarray, how could any rational governing body logically pursue a similar strategy against a country over three times the size, with a complex topography and an equally diverse ethnic and religious landscape? The Iranian regime, while imperfect, does maintain a general stasis between the varied sects of Shia and Sunni Muslims in the country. Under the chaos of war and foreign-military occupation, the outbreak of sectarian warfare like that of Iraq is a real possibility, made worse by the virulently anti-Shia Al Qaeda and ISIS waiting at the periphery. Prolonged and extensive carnage would surely follow.
Further complicating such a campaign would be the presence of the Marxist guerilla cult and U.S. foreign-policy establishment favorite, the Mujahideen-e Khalqh (MEK), who would also be vying for control of the state, despite that their popular support inside Iran is approximately nonexistent. The combination of these factors seriously diminishes the long-term probability of success for a U.S. invasion of Iran.