By 2017, after six years of civil war, Bashar al-Assad’s Syria had settled into a new normal. It wasn’t the placid, pre-Arab Spring normal the Assad family had enjoyed ever since cracking down on an Islamist insurgency in the 1980s, but it was something. With help from Russia, Iran, and Hezbollah—and in a strange way, the United States, which was attacking ISIS—Assad’s forces had succeeded in beating back the rebels. As the years went on, his regime came to control roughly two-thirds of Syria.

Secure in power, Assad started traveling abroad, visiting Moscow, Beijing, Abu Dhabi, and Tehran. Everyone seemed to begrudgingly accept that the brutal strongman was here to stay, with “normalization” the watchword not only among Middle Eastern diplomats but even some Western ones. In September, after a thirteen-year diplomatic freeze, Italy appointed its first ambassador to Syria.

But then, on Saturday, after a ten-day-long surprise offensive by the rebel group Hayat Tahrir al-Sham, that stability vanished. The Syrian Arab Army melted away, with soldiers abandoning their posts and stripping off their uniforms. The rebels took Damascus without a fight, and Assad was spirited away to Moscow. Even the opposition was surprised by how easy it all was.

The sudden, unexpected surrender of the Syrian army is part of a long tradition of outwardly strong, inwardly brittle armies quickly collapsing in the face of rebel advances to nearly everyone’s surprise. Most recently, in Afghanistan in 2021, the Afghan National Army—trained and equipped by the United States to the tune of $83 billion over two decades—folded in a matter of months as the Taliban surged to power. Before that, in Iraq in 2014, the country’s military crumbled as ISIS took over much of the country, including the cities of Fallujah and Mosul. That same year, Houthi rebels in Yemen seized the capital, Sanaa, in just days, and soon toppled the government of Abdrabbuh Mansur Hadi, who fled to Saudi Arabia.

Further afield, the same phenomenon occurred in the Central African Republic in 2013, when the Séléka coalition of rebels overthrew the government in a matter of months, seizing the capital, Bangui, with little resistance. The country’s embattled president, François Bozizé, slipped away to Cameroon. To the south, in Zaire, the forces of Mobutu Sese Seko fell apart in 1997 as a rebellion from the east swept the country. With the rebels closing in on his jungle palace, Mobutu, who had been in power since the 1960s, fled for Morocco. His own disgruntled presidential guards took potshots at the fuselage of his getaway plane as it took off.

The timing of collapse is always impossible to predict; in the game of Jenga, you never quite know which removed block will bring the whole tower tumbling down. But the causes of collapse can always be cataloged. Again and again, the same factors hollow out militaries fighting insurgencies.

The first is ethnic exclusion. Governments often fill their armies, especially the top brass, with their ethnic brethren. There are advantages to this approach—greater cohesion and loyalty—and it’s a time-tested way of “coup-proofing” a regime. In civil wars with an ethnic dimension, it’s often unavoidable that government forces come from one group and rebels from another. But the practice inevitably generates resentment among those groups on the outside.

In Zaire in the early 1990s, half of the army’s generals hailed from Mobutu’s own province, and a third of those were fellow members of his relatively small ethnic group, the Ngbandi. In the Central African Republic, one of the rebels’ main grievances was that the government had refused to integrate certain ethnic groups into the military. Yemen’s Shiites felt their concerns were ignored under Hadi, a Sunni. Before the rise of ISIS, Iraq’s military under Prime Minister Nouri al-Maliki marginalized Sunnis. In the Afghan National Army, Tajiks at one point accounted for more than two-thirds of commanders, even though they made up only a quarter of the population.

In Syria, some 70 percent of all soldiers and 80 percent of all officers were members of Assad’s Alawite sect, even though the group made up just 13 percent of the population. The Alawites’ dominance was near total in the Republican Guard, the elite protection group commanded by one of Assad’s brothers. The non-Alawite conscripts in the lower ranks turned out to have little interest in dying for an officer corps and a regime that did not represent them.

Then there is corruption, a powerful corrosive agent that erodes armies. Weak governments often can’t afford the salaries necessary to buy their forces’ loyalty, so they tolerate or unwittingly encourage graft. Mobutu, who once instructed his followers to “steal cleverly, little by little,” twice presided over mass pillages carried out by angry unpaid soldiers.

In the Yemeni, Iraqi, and Afghan armies, positions went not to the most qualified but to those who had connections or were willing to pay a bribe. The payrolls were filled with thousands of “ghost soldiers,” nonexistent positions created to allow commanders to embezzle salaries. In Afghanistan, corrupt air force officers were suspected of smuggling opium and guns. Many of the Afghan military’s commanders were warlords who had once been aligned with the Taliban and whose allegiance was for sale to the highest bidder. When the Taliban swept across the country in 2021, in many areas it didn’t have to fight; all it had to do was pay off security officials and watch their troops surrender.

The Syrian army was also riddled with corruption, ranging from the extortion of petty bribes from cars passing through checkpoints to a multi-billion-dollar enterprise that produced and sold captagon, an illegal amphetamine. The rank and file complained about officers who stole their fuel subsidies and insisted that soldiers who wanted to take leave pay for the privilege.

Corruption within militaries aggravates the population whose support rebels feed off of. It also makes militaries less effective by diverting resources away from investments in weapons, equipment, and salaries for troops, and it alienates the lower ranks. As an Afghan official told the authors of a U.S. government report on the collapse of the Afghan army, “Nobody wanted to die for … people who were here to rob the country.” The same proved true in Syria. The last-minute promise Assad made to give Syrian soldiers a 50 percent pay raise was hardly enough to revive morale.

But the most consequential factor behind recent army collapses is external rather than internal: the loss of foreign patrons. Weak governments usually need help maintaining controlling territory, and when outsiders pull the plug, their withdrawal of support can be that final Jenga block.

It was no coincidence that Zaire’s army collapsed after the Cold War when the United States no longer had any use for Mobutu and unceremoniously dumped him as an ally. In the Central African Republic, France, the former colonial power, had come to the rescue as the government fought rebels before, but in 2013, it made it clear it wouldn’t do so again. When the Yemeni military was on the verge of implosion, the United States, which had helped the government battle Al Qaeda in the Arabian Peninsula, declined to extend its counterterrorism support to fighting the Houthis. In both Iraq and Afghanistan, similarly, it was the withdrawal of U.S. forces that precipitated the collapse of the army (just as it had been in South Vietnam long before).

The proximate cause of the Syrian army’s evaporation was the sharp reduction in foreign support. Russia was tied up in Ukraine; its air force was unable to repeat the barrage of airstrikes that had rescued Assad back in 2015. Hezbollah was staggering from Israel’s strikes against it in Lebanon, including the exploding-pager attack, and could no longer supply the number of fighters it once had. Iran, too, was licking its wounds from Israeli strikes and quickly withdrew its military forces from Syria.

The armies of unrepresentative governments are often microcosms of their regimes. Like the Syrian military, the Syrian state was brittle, hollowed out by years of corruption and exclusion, and barely propped up by outside support. In retrospect, what was remarkable was not how quickly the regime fell, but how long it managed to last.

Stuart Reid is a senior fellow at the Council on Foreign Relations and the author of The Lumumba Plot.

Image: Hussein Kassir / Shutterstock.com