Jafari heads the Iranian Revolutionary Guard Corps, a full-blown army of some 300,000 personnel (not counting reservists). The IRGC is the most powerful element in the regime's security forces, running everything from the country's missile systems to the Basij militia, whose hundreds of thousands of young men enforce domestic order and have been at the forefront of attacks against those protesting the election result. Reporting to the Supreme Leader, the IRGC is listed by the U.S. government as a terrorist organization — and also maintains an extensive business empire in Iran. It is believed to be a base of support for Ahmadinejad, although one of the Corps' influential former commanders, Mohsen Rezaei, ran against the incumbent in the election (finishing fourth, according to official results). The support of the IRGC and the Basij will be crucial to the regime's hopes of suppressing a popular revolt against the election result.
— Scott Macleod