How does an authoritarian regime die? "Gradually, then suddenly," Ernest Hemingway once wrote, though he was reflecting on bankruptcy. 

For weeks, Iranians chanted against their rulers, while supporters abroad hoped the Islamic Republic was approaching that stage of "sudden" collapse. 

But what happened instead was methodical repression. So, if the regime in Tehran is decaying, it is still doing so gradually. The main reason for its survival is a single institution — the Islamic Revolutionary Guard Corps (IRGC).

Iran is enduring one of its most serious internal crises in years. Nationwide protests erupted amid deep economic distress, political suffocation and long-simmering anger. The unrest began against the backdrop of military pressure from the US and Israel over the past two years, but for ordinary Iranians, the more immediate blow has been economic. 

Sanctions have bitten hard. The UK, Germany and France reimposed all UN sanctions that had been lifted under the now-defunct 2015 nuclear deal. By 2025, food price inflation had surged beyond 70%. In December, the rial slid to a record low.

Despite this pressure, the regime has not cracked. The reason is less in ideology and more in organisation.

Since the Islamic revolution of 1979, Iran's rulers have invested heavily in building a parallel military organisation. Today the IRGC is the most important organisation in the country, with an explicit mandate to defend the ideology and governing system born out of the revolution. It answers not to the government but directly to the supreme leader, Ayatollah Ali Khamenei.

During the disputed presidential election of 2009, I watched the IRGC and Basij dismantle a mass movement with chilling efficiency. Basij volunteers lined Tehran's streets armed with rubber truncheons and wooden clubs. Behind them stood uniformed men carrying automatic weapons. Motorcycle squads roared down the city's broad avenues, swooping on any group attempting to gather.

The IRGC has an estimated 150,000 men under arms and operates alongside, often above Iran's conventional armed forces. Over decades, it has embedded itself deeply within the economy, controlling or influencing vast commercial interests. Power, money, corruption, and ideology intertwine here, giving the organisation every possible incentive to preserve the status quo.

So, when protests began, it was the IRGC that mattered most.

In the past two weeks, IRGC forces obeyed orders to fire on their fellow citizens. Demonstrations that once surged through cities have now ended, as far as can be determined in a country where the authorities continue to impose a communications blackout. 

On the front line of repression is the IRGC's auxiliary force, the Basij militia, a volunteer paramilitary organisation that claims millions of members. Western estimates suggest its active-duty contingent alone runs into the hundreds of thousands. It is the Basij that typically confronts protesters face to face, delivering the regime's violence at the street level.

"During the disputed presidential election of 2009, I watched the IRGC and Basij dismantle a mass movement with chilling efficiency. Basij volunteers lined Tehran's streets armed with rubber truncheons and wooden clubs. Behind them stood uniformed men carrying automatic weapons. Motorcycle squads roared down the city's broad avenues, swooping on any group attempting to gather," British journalist Jeremy Bowen wrote in a BBC article.

"Within less than two weeks, protests that had paralysed the capital were reduced to pockets of defiance, students chanting slogans, rubbish bins set alight. At dusk, people stepped onto balconies and rooftops to shout 'God is greatest', echoing the chants once used against the Shah. Even that faded," Jeremy Bowen recalled.

The lesson was clear then, and it remains so now: When ordered, the IRGC and its auxiliaries act decisively without hesitation.

This apparent resilience does not mean Tehran feels secure. Ayatollah Khamenei and his inner circle know that loyalty must be constantly reinforced. Millions of Iranians who want the regime gone are seething with resentment. The pressure from abroad has not disappeared either. US President Donald Trump continues to threaten action, even as Tehran mixes bellicose rhetoric with tentative signals about resuming negotiations.

Talks could buy Iran time. A comprehensive deal on nuclear ambitions and ballistic missiles has defeated multiple rounds of diplomacy before, but the mere prospect of negotiations may serve a purpose. 

Trump has warned that he will impose a 25% tariff on goods from any country doing business with Iran. China remains Iran's biggest oil customer, and Trump and President Xi Jinping agreed a truce in their trade war last autumn, with a summit scheduled in Beijing in April. Whether Washington would disrupt that process to tighten pressure on Tehran is an open question.

Inside Iran, the supreme leader's priority now is survival. Any further eruptions of protest can expect a severe response. 

One advantage for the regime is the opposition's lack of coherent leadership. The eldest son of the Shah, deposed nearly half a century ago, has attempted to fill that vacuum. But his appeal is constrained by his family's history and his close ties to Israel.

Still, history offers unsettling reminders. In late 2024, Syria's Bashar al-Assad, long propped up by Iran and Russia appeared to have won his war and was being slowly rehabilitated by Saudi Arabia and the Arab League. 

Then a well-organised rebel offensive struck. Neither Tehran nor Moscow intervened. Within days, Assad and his family fled to exile in Moscow.

In Tunisia in 2011, President Zine El Abidine Ben Ali fell when the army chose to protect protesters rather than the regime's internal security forces. His collapse triggered Hosni Mubarak's resignation in Egypt. Mubarak might have survived mass demonstrations had the armed forces not concluded that sacrificing him was necessary to save themselves.

That is the scenario Iran's rulers most fear.

For now, the IRGC remains loyal and deeply invested in the system it protects. As long as that remains true, the Islamic Republic is unlikely to collapse suddenly.

IRGC / Islamic Revolution Guards Corps (IRGC) / Iran / Iran protest