"Iran's national security policy is the product of many, and sometimes competing, factors: the ideology of Iran's Islamic revolution; Iranian leadership's perception of threats to the regime and to the country; long-standing Iranian national interests; and the interaction of the Iranian regime's various factions and constituencies. Some experts assert that the goal of Iran's national security strategy is to overturn a power structure in the Middle East that Iran asserts favors the United States and its allies Israel, Saudi Arabia, and other Sunni Muslim Arab regimes. Iran characterizes its support for Shiite and other Islamist movements as support for the 'oppressed' and asserts that Saudi Arabia, in particular, is instigating sectarian tensions and trying to exclude Iran from regional affairs. Others interpret Iran as primarily attempting to protect itself from U.S. or other efforts to invade or intimidate it or to change its regime. Its strategy might, alternatively or additionally, represent an attempt to enhance Iran's international prestige or restore a sense of "greatness" reminiscent of the ancient Persian empires. From 2010 until 2016, Iran's foreign policy also focused on attempting to mitigate the effects of international sanctions on Iran."
CRS Report for Congress, R44017
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html