The country formerly known as Persia became Iran in 1935, and became an Islamic republic in 1979 following the overthrow and exile of the previous ruling monarch. The ultimate political authority rested in the power of the Supreme Leader, a learned religious scholar who reigned in the theocratic government established by conservative clerical forces.

In November of 1979, a group of Iranian students overtook the US embassy in Tehran (and held it for a little over a year), which was the beginning of the strained relationship between these two nations. Significant bloodshed occurred between Iran and Iraq in the '80s, a struggle that expanded to the Persian Gulf and US involvement in the latter part of the decade.
As a result of their actions in various regions and their nuclear armament, Iran has been identified as a state sponsor of terrorism. Following the realization of the popular dissatisfaction with the Iranian regime, their began a campaign for political reform which faltered with the repressive rule of conservative politicians and prevention of these efforts by said politicians.
The elections for Iran's elected government institutions in 2003 and 2004 found the conservatives back in power, electing Mahmud Ahmadi-Nejad as president in 2005.

Iran has been very stubborn as far as nuclear weaponry goes, having been encountered with several resolutions from the UN Security Council calling for the suspension of uranium enrichment and the compliance with certain related obligations and responsibilities.
Iran is currently involved in many disputes on the international playing field. With Afghanistan, Iran has qualms with the diverting of the Helmand River during drought. With Iraq, Iran argues the jurisdiction beyong the mouth of the Shatt al Arab in the Persian Gulf. With UAE, Iran is working to settle disputes over their occupation of Tunb Islands and Abu Musa Island. With regards to the Caspian Sea, Iran desires a five-way split of the oceanic territory. All in all, Iran is a quite the international squabbler. Their policies on international relations are based on eliminating outside forces and persuing diplomatic relations with developing and non-aligned countries. A member of the UN, Iran is diplomatic with all other member countries excepting Israel and the US.
http://en.wikipedia.org/wiki/Iran
https://www.cia.gov/library/publications/the-world-factbook/geos/ir.html
http://www.travelblog.org/Middle-East/Iran/fact-int-iran.html