Iran, State Sponsor of Terrorism:
Iran has consistently been described by the United States as the world's foremost state sponsor of terrorism. It actively supports terrorist groups, most prominently the Lebanese group Hezbollah. The Iranian relationship with Hezbollah demonstrates one accepted explanation of why states sponsor terrorism: to indirectly influence politics elsewhere.
According to Michael Scheuer, former CIA officer:
State-sponsored terrorism came in the middle-1970s, and ... its heyday was in the 1980s and early-'90s. And typically, the definition of a state sponsor of terrorism is a country that uses surrogates as its weapon to attack other people. The primary example to this day is Iran and Lebanese Hezbollah. Hezbollah, in the nomenclature of the discussion, would be the surrogate of Iran.
Islamic Revolutionary Guard Corps:
The Islamic Revolutionary Guard Corps (IRGC) was created following the 1979 revolution to protect and promote the objectives of the revolution. As a foreign force, they have also exported that revolution, by training Hezbollah, Islamic Jihad and other groups. There is evidence that that IRGC is playing an active role to undermine Iraq, by funneling funds and arms to Shiite militias, engaging directly in military activity and gathering intelligence. The extent of Iranian involvement is not clear.
Iran and Hezbollah:
Hezbollah (which means Party of God, in Arabic), an Islamist Shiite militia based in Lebanon, is a direct product of Iran. It was formally established in 1982 following the Israeli invasion of Lebanon, aimed at uprooting the PLO (Palestinian Liberation Organization) bases there. Iran sent Revolutionary Guard Corps members to assist in the war. A generation later, the relationship between Iran and Hezbollah is not entirely transparent, so it is not clear whether Hezbollah should be considered a full proxy for Iranian intentions. However, Iran funds, arms and trains Hezbollah, in large part through the IRGC.
According to the New York Sun, Iranian Revolutionary Guard soldiers fought alongside Hezbollah in the Israel-Hezbollah summer 2006 war, by supplying intelligence on Israeli targets and manning and firing missiles.
Iran and Hamas:
Iran's relationship with the Palestinian Islamist group Hamas has not been constant over time. It has, rather, waxed and waned according to the interests of Iran and Hamas at different times since the late 1980s. Hamas is the dominant political party in the Palestinian territories that has long relied on terrorist tactics, including suicide bombing, to register protest with Israeli policies.
According to Cambridge University Professor George Joffee, Iran's relationship with Hamas began in the 1990s; it was around this time that Iran's interest in exporting revolution coincided with Hamas' rejection of compromise with Israel. Iran has been alleged to provide funding and training for Hamas since the 1990s, but the extent of either is unknown. However, Iran did pledge to help fund the Hamas led Palestinian government after its parliamentary win in January 2006.
Iran and Palestinian Islamic Jihad:
The Iranians and PIJ first made extended contact in the late 1980s in Lebanon. Subsequently, Islamic Revolutionary Guard Corps trained PIJ members at Hezbollah camps in Lebanon and Iran commenced funding PIJ.
Iran and Nuclear Weapons:
The creation of WMD is not itself a criteria for being a state sponsor of terrorism, however, when already designated state sponsors appear to have manufacturing or acquisition capabilities, the U.S. grows especially worried because could be transferred to terrorist groups. At the end of 2006, the United Nations adopted Resolution 1737, and imposed sanctions on Iran for failing to halt its uranium enrichment. Iran has contended that it has that right, in order to create a civil nuclear program.