What the U.S. military thinks about Iran
From the Pentagon's most recent assessment (pdf):
'There has been no change to Iran's strategies over the past year. Iran's grand strategy remains challenging U.S. influence while developing its domestic capabilities to become the dominant power in the Middle East. Iran's security strategy remains focused on deterring an attack, and it continues to support governments and groups that oppose U.S. interests. Diplomacy, economic leverage, and active sponsorship of terrorist and insurgent groups, such as Lebanese Hizballah, Iraqi Shia groups, and the Taliban, are tools Iran uses to increase its regional power. Iran's principles of military strategy remain deterrence, asymmetrical retaliation, and attrition warfare. '