Since its inception in 1979, the Islamic Republic of Iran's nezam (establishment) has faced internal and external threats without interruption, some of them existential. These threats have included the eight-year Iran-Iraq War, the Kurdish armed insurgency, coup plots — the government barely escaped the Nojeh coup plot in 1980 — massive popular uprisings and foreign subversive efforts. The 1979 seizure of the US Embassy in Tehran and the hostage crisis that followed prompted the US doctrine of “regime change” towards Iran. To that end, the US relied on a combination of, among other things, supporting Iraq during perhaps the bloodiest Middle East war of the 20th century, subversion policies, draconian sanctions, covert operations and support of militant groups. Some aspects of the sanctions imposed on Iran were unprecedented in modern history. In order to incite internal opposition in Iran, the US sought to support and finance “Iranian exile networks in and out of Iran and an exile radio station that broadcast propaganda about Iran's government,” according to a report in the New York Times. Domestically, the Iranian government has faced armed struggles by militant and ethnic groups, primarily the Kurds, and two major popular uprisings, one in 1999 and the other in 2009. The latter, which marked the emergence of the Green Movement, was considered by Mohamed Ali (Aziz) Jafari, commander of the Islamic Revolutionary Guard Corps (IRGC), to be “a threat way more dangerous than the eight-year war” with Iraq. In the aftermath of the 2009 upheavals, then-US secretary of state Hillary Clinton said, “Behind the scenes, we were doing a lot . . . We were doing a lot to really empower the protestors without getting in the way.” So why, despite the intensive efforts by internal and external forces, has the system not collapsed? There are five explanations. The first is repression. The opposition asserts that repression, intimidation and harsh prison sentences have maintained the system. As a glaring example, they refer to the forceful suppression of the 2009 mass demonstrations. Many people were arrested and received long jail sentences, and the two leaders of the movement have been under house arrest since 2010. Against this theory, some point to the former shah's regime, which was toppled by the 1979 Revolution, and East European communist regimes, both of which used similar tactics yet could not quash revolts. Each of these used brute force against opponents but fell nonetheless. Yet this has not happened in Iran. So there must be other factors involved in holding the system up, some argue. The second explanation is the lack of any popular alternative. In the last 37 years, no opposition leader or political current that has sought to overthrow the regime, either inside or outside of Iran, has gained significant popularity among the Iranian opposition. Charisma is a quality that none of the opposition leaders appear to have had. But more importantly, they have all sought to mobilise people against the government by calling for freedom and social and political liberties. Ayatollah Khomeini, the leader of the revolution, mobilised the masses by focussing on social justice and by defending the “barefoot,” the mostazafin. “Freedom” was one of the central slogans of the Iranian Revolution, but not the only one. For better or for worse, the masses viewed the “Islamic” system as one that would fulfill every aspect of social justice in its broad meaning, including economic. Central to Khomeini's discourse was his defence of the kookh'neshinan (those who live in very poor accommodation) against the kakh'neshinan (those who live in palaces). Calls for social and political freedom can absorb middle- and upper-middle class urbanites, but these are hardly prepared to make dangerous and enduring sacrifices, especially when their opponents are ready to use brute force and are prepared to make sacrifices for their religious beliefs. For example, the Green Movement failed to make economic demands, suggesting that its social base was the middle- and upper-middle class. The movement was not seeking justice for the disadvantaged and the poor. Such a movement can only go so far in Iran. The third explanation for the survival of the Islamic regime is the lack of a patron-client relationship with foreign powers. The Iranian regime has been able to thwart foreign dominance. This was one of the major fronts in the quarrel between the former shah and the opposition, who argued that the shah was an American puppet. Some among the contemporary opposition have resorted to conspiracy theories, but none have presented convincing evidence in support of their claims, nor have they been able to explain the reason behind the imposition of crippling sanctions on Iran by the United States. The fourth is the election mechanism. Elections in Iran appear as a mechanism for the populace to impose their will against that of the establishment despite obvious restrictions, including the vetting of candidates by the country's Guardian Council. The elections of 1997 and 2013 are glaring examples. Against all predictions by Western experts, two moderates, Mohamed Khatami and Hassan Rouhani, were elected as president in landslide victories. The fifth is grassroots support. What preserves the system is its grassroots support among conservative Shias. No transparent polling is available to provide an accurate figure of those who are opposed to the regime and those who support it. After the 2009 presidential elections that resulted in the victory of Mahmoud Ahmadinejad, who at the time represented the conservative camp, the Washington Post published an article that stated: “While Western news reports from Tehran in the days leading up to the voting portrayed an Iranian public enthusiastic about Ahmadinejad's principal opponent, Mir Hossein Mousavi, our scientific sampling from across all 30 of Iran's provinces showed Ahmadinejad well ahead.” The article was co-authored by US commentator Ken Ballen, president of the US pressure group Terror Free Tomorrow, which studies attitudes toward extremism, and Patrick Doherty of the New America Foundation. Regardless of which camp has the majority, the reality is that Iranian society is fragmented between the forces of tradition (conservatives) and modernity (liberal Muslims and secularists). It is also a reality that both factions are large and cannot be ignored. The conservatives support the system wholeheartedly and consistently, partly because of their religious beliefs and partly because they enjoy advantages that their opponents do not. They are considered khodi, or insiders, by the system, while the rest are considered nakhodi, or outsiders. These social forces are present at all levels of society, from governmental offices to schools, universities and industrial complexes. In the case of any upheaval by an opposing camp, they, especially the youth vigilante groups, will counter it by using force, as well as with large demonstrations. They obviously have the support of the security apparatus, the IRGC and the police. This force is the main element that explains the staying power of the Islamic Republic of Iran, together with the role of Islam in the mobilisation of the people. The writer is a political analyst who writes on Iranian domestic and foreign affairs.