Aleppo, once Syria's most populous city, has fallen back into the bloodied hands of Syrian dictator Bashar Assad. This victory comes not because Assad somehow inspired Syrians to unite under him to save their country, but because he imported armies of thugs from Russia, Iran and Lebanon's Hezbollah.

Reports from Aleppo suggest Assad's loyalists continue bombarding civilian areas and going door to door, gunning down women and children. The U.N. called it "a complete meltdown of humanity." If the reports are confirmed, a war crimes tribunal must follow. Those responsible, including Assad himself, must answer for the atrocities.

Victory came at a heavy price. Aleppo once was home to 2 million people. Now it has been destroyed. Millions have been left homeless and destitute, hundreds of thousands have been killed or maimed.

Assad has tried hard, just like Saddam Hussein did in Iraq, to put the patina of benevolence on his iron-fisted rule. But no one is fooled. He has never allowed democratic elections. He inherited his title of "president" from his father, Hafez Assad, who massacred tens of thousands of civilians in the city of Hama in 1982. His military occupation of Lebanon ensured perpetuation of its 15-year civil war and gave birth to the Hezbollah movement.

Bashar Assad learned at the feet of his father. He owes his survival not to popular support, but to massive firepower and air bombardments from Russian forces, backed by Iranian and Hezbollah ground troops.

The fall of Aleppo may have dealt the rebels a potential death blow. Part of President Barack Obama's reluctance to become more deeply involved at the early stages of the civil war was the ill-defined nature of the rebel movement. They had a fractured message and appeared to be fighting for divergent causes. Some favored secular governance, but others favored replacing Assad's government with hard-line Islamic rule.

The prospect of Islamic State fighters gaining the upper hand helped motivate Russia to intervene on Assad's behalf with grudging U.S. acquiescence.

Many, if not most, Syrians wanted Assad gone, but the prospect of a hazy future under a bickering hodgepodge of militia leaders hardly seemed an appealing alternative. The lessons of chaotic outcomes in Lebanon and Iraq are far too fresh on Syrians' minds, which might have caused many to reject the rebel cause. The only option was reunification under Assad's rule.

The ends of Assad's backers never justified their means, including the use of chlorine-gas barrel bombs in 2015.

Just as murderous militia leaders temporarily escaped accountability in the Balkans following Yugoslavia's disintegration, there are ways for persistent war-crimes investigators to ensure that no one in Syria's leadership escapes justice. Just as Radovan Karadzic and Slobodan Milosevic ultimately had to answer for their actions, so, too, must Bashar Assad.

REPRINTED FROM THE ST LOUIS POST DISPATCH