BEIRUT • The Syrian civil war, and the intense new ground battle in the divided city of Aleppo, is often seen as a contest between a chaotic array of rebel groups and the Russian-backed government of President Bashar Assad.
But the reality is that Mr Assad's side is increasingly just as fragmented as its opponents, a panoply of forces aligned partly along sectarian lines but with often-competing approaches and interests.
There are Iraqi Shi'ite militiamen cheering for clerics who liken the enemy to foes from seventh-century battles. There are Iranian Revolutionary Guards fighting on behalf of a Shi'ite theocracy. There are Afghan refugees hoping to gain citizenship in Iran, and Hizbollah militants whose leaders have long vowed to fight "wherever needed".
The Syrians themselves are in a few elite units from an army steeped in a nominally socialist, Arab nationalist ideology, exhausted after five years of war, as well as pro-government militias that pay better salaries. And, yes, overhead there are the Russian pilots who have relentlessly bombed the rebel-held eastern side of Aleppo - trained to see the battle as supporting a secular government against Islamist extremist terrorists.
"The government's fighting force today consists of a dizzying array of hyperlocal militias aligned with various factions, domestic and foreign sponsors, and local warlords," said one analyst, Mr Tobias Schneider, in recently summing up the situation.
The battle for eastern Aleppo, where the United Nations says some 275,000 people are besieged, has raised tensions between the United States and Russia to their highest levels in years, but the Cold War rivals do not wield clear control over their nominal proxies.
The competing interests on both sides and lack of clear leadership on either one is part of why the fighting has proved so hard to stop.
Mr Assad is desperate to retain power, Russia is seeking to increase its clout at the global geopolitical table, Iran is exercising its regional muscle, Afghan fighters seek citizenship in Iran, and leaders of Hizbollah, the Lebanese Shi'ite militia, have always vowed to go "wherever needed" to prevail in the war.
While both Washington and Moscow say preservation of Syrian state institutions is a priority, a look at the fight for Aleppo, Syria's largest city, shows that those structures are already atrophying.
At least one elite Syrian army unit has been filmed seizing positions in Aleppo, but the bulk of the pro-government force is made up militiamen trained and financed by Iran, the Shi'ite theocracy that is the Syrian government's closest ally, according to experts, diplomats, regional officials and fighters battling for and against the government.
"Aleppo is Shi'ite, and she wants her people," goes a song overlaid onto a video clip posted online of an Iraqi cleric visiting Iraqi Shi'ite militia fighters on the front lines south of Aleppo. The message ignores the fact that the mainstream Shi'ite sect that makes up the bulk of the Iraqi militias accounts for less than one per cent of Syria's population.
The government's Aleppo offensive has moved aggressively in the past week, worsening a humanitarian crisis. Syrian or Russian airstrikes have hit seven hospitals and have killed hundreds of civilians, in what Moscow and Damascus describe as preparation for a final battle for the city.
There is more cultural affinity between Russia and senior Syrian army officers - steeped in secular Baathist ideology and often trained in the Soviet Union - than between Syria's formal military and Iran and Hizbollah. But militarily, they are all interdependent.