Why Iran acts the way it does

Currently, Iran is probably the most dicussed actor in international relations. An emerging power with a big population, strategic position, oil ressources and nuclear ambitions, they are of concern to many policymakers around the world. Being an internationally isolated theocracy, however, they are often pictured as an irrational threat. It is therefore important to ´look closely at their foreign relations and determine which factors contribute to their actions being the way they are.

History
Iran, being an international power long ago, lost territory and influence in the 19th century to the British and the Russian Empires. Since then, they remained at least partly under foreign control for almost a century. Three major shifts occured: First, the constitutional revolution installed a parliament in the early 20th century. Second, in 1951, Prime Minister Mossadeq tried to nationalise the oil industry and was overthrown by a military coup supported by the CIA and MI6 (Operation Ajax). Finally, in 1979, the Islamic Revolution was successful in ending the US-backed monarchy and establishing most parts of the system we know until today.
During this revolution, the US embassy was seized, and 52 Americans were hold hostage for almost two years. This increased the already isolated situation of the new regime and is the main reason for hostilities between Iran and the US in the 80s. During this crisis, Iraq tried to invade Iran, leading to 8 years of war, about a million deaths, economic losses and further Iranian alienation, as Iraq was backed by many countries. In the 90s, the US accused Iran of supporting terrorism. At the same time, accusations that Iran was developing nuclear weapons started and have been an issue since, even though Iran agreed on nuclear inspections. Ever since the Islamic Revoltion, Iran has gone from sanction to sanction; because of the Hostage Crisis; because of sponsoring terrorism; because of developing nuclear weapons.
After the elections in 2009, mass protests started in Iran because of alleged voter fraud, and have been cracked down by authorities.

Political System
Contrary to popular belief, Iran is not a mere theocracy with a single dictator. It has a complex political system, with a strong bureacracy, both overlaying religious institutions and underlying religious themes, a Prime Minister, military groups and a parliament, to name only parts of it. As it is almost impossible to describe the details of this system, and as especially the informal policy process changes over time, I will concentrate on some major institutions and actors.
The most important actor is the Supreme Leader. He has control over the military, the media, the justice system and he is a religious authority. He also appoints members of the Guardian Council. However, most of his power and control over institutions does not rely on institutional power, but on his informal authority, meaning his „presumed moral authority and his skillful orchestration of informal networks“ (Green, Wehrey, Wolf, 2009: p 31). His informal power is strengthened by the fact that he can stay in power until he dies or the Assembly of Experts dismisses him. That way, he has decades to build up networks.
Through the Guardian Council, it is regulated who can run for public office. The GC can prevent candidates from doing so, and it has not hesitated in the past to use its power. Because of the, both the elections for President and Parliament are not entirely free. The GC, as well as the Supreme Leader, can veto parliamentary decisions. In other terms, not only does it determine who has a chance to get into parliament, it also has the last word on every legislation parliament might pass. Because of that, the role of parliament is limited. However, parliament does appoint part of the members of GC, creating some sort of mutual control, and members of parliament try to excert power on different levels through more informal channels.
The President is the head of government, and as such, he has control over the bureacracy and oversees the implementation of legislation. As seen recently (compare The Economist, 2011), he can be in a power struggle with the Supreme Leader, and while the latter is the stronger one (for example, he can hardly lose office), they both wield power and can each cause damage for the other.
As Ehteshami points out, the public opinion also plays a role in foreign policy, and there are a variety of newspapers, although most are state owned or under some sort of state control (Ehteshami, 2002: p 296).
To sum this up, we have a central authority (Supreme Leader), but also many different power bases and factions, all of which struggle and create the need for compromise. This and the continuity due to the bureaucracy and the Supreme Leader make Iran a rational actor whose actions can, to some extent, be anticipated by looking at previous actions.

Foreign Policy
While looking closely at the foreign policy of Iran, we will see 4 different themes that overlay they main strategies.
First of all, every revolutionary country has similar foreign policy goals. Ever since the French Revolution, we have seen a determination by such governments to a) defend the revolution and b) spread it. Since such revolutions are aimed against authoritarian governements, other authoritarian governments in the region will become aware of the chance of revolution, causing a determination to end any revolution anywhere and a stricter domestic policy towards unrest. From the revolutionary countries view, however, it is surrouned by hostile governments, while it is the isle of freedom. It has to spread the values not only because it deems them universal, but also because its current neighbours are a threat.
This theme will explain why many countries, especially the Arab countries, were eager to support Iraq in their war against Iran – they hoped to contain the revolution. It will also explain why Iran is supporting foreign revolutionary groups like the Hizbollah.
Furthermore, it is one of the reasons Iran has been cautious in opening up, as it is afraid of any changes to its system (Green/Wehrey/Wolf 2009) and of foreign influence.
During the Arab Spring, the Iranian government even tried to interprete it as a late effect of the Islamic Revolution, hoping to appeal to Islamic groups and apear as a role model. While this would in theory increase Irans influence on those kinds of governments, it seems unlikely that the Arab Revolutionaries will adapt Irans model. In fact, Egypts president Mursi publicly criticised Syria, Irans closest ally, causing tensions. This was perceived as an ideological struggle between Egypt and Iran about the nature of the Arab Spring.
Meanwhile, Iran has suppressed protests in its own country.
The second theme is that of Irans isolation and its attempts to break this. It is no secret that there are US bases, troops and allies all around Iran. Ever since the revolution and the hostage crisis, the US has been Irans main enemy except for Iraq. And even without the US, Irans relations to its Arab neighbours are often hostile, increasing the feeling of being súrrounded and increasing Irans need for security.
The Invasion of Afghanistan and Iraq removed two of Irans biggest enemies, namely the Taliban and Saddam. Instead, they got US forces – however, as these forces eventually leave, both countries will offer oppurtunities for Iran to excert influence in the region and finally break the circle.
Irans only ally in the region, Syria, is important because it offered Iran the only route to the Arab world. Through Syria, Iran could assess Lebanon, the Hibzollah and its Palestinian allies. With Syria weakening, Iran might lose its main chance at breaking the islolation, which is why Iran is supporting the Assad regime.
Non state actors (ideology)
petropolitics

References:
Scholars:
Ehteshami, A. (2002): The foreign policy of Iran, in The foreign policies of Middle East states. Boulder, Co.: Lynne Rienner, pp. 283-309.
Green, J; Wehrey, F.; Wolf, C. Jr. (2009): Understanding Iran, RAND Corporation, Santa Monica, CA

Articles:
http://www.britannica.com/EBchecked/topic/293359/Iran
International: President v supreme leader; iran’s politics. (2011, Nov 05). The Economist, 401, 56-56.
http://www.pbs.org/wgbh/pages/frontline/shows/tehran/axis/map.html
Maps: US bases encircle Iran (2012, May 01) Al Jazeera Online :
http://www.aljazeera.com/indepth/interactive/2012/04/2012417131242767298.html