The Pentagon announced on Wednesday that the last American troops had left Iraq, more than two decades after the US invaded the country.

A handover ceremony at Erbil Air Base in the northern Kurdish region marked the end of the US military presence.

The administration of then-President George W. Bush justified the 2003 invasion by claiming that longtime Iraqi leader Saddam Hussein possessed weapons of mass destruction. Washington never substantiated the allegations, while Iraq descended into a quagmire of violence involving Sunni and Shia Muslims as well as Kurds.

US forces pulled out in 2011 amid a slew of war crimes allegations, including the killing of unarmed civilians.

According to some estimates, more than a million Iraqis lost their lives as a result of the conflict, with millions more displaced.

Left in disarray with a weak central government and security forces, Iraq became fertile ground for Islamist militant groups. The crisis came to a head with the emergence of Islamic State, which seized around a third of Iraqi territory and spread into several neighboring countries, proclaiming a ‘caliphate’. Its militants massacred those they deemed insufficiently Muslim, as well as Christians and members of other religious minorities.

Washington intervened again in 2014 with a deployment code-named Operation Inherent Resolve.

RT correspondent Steve Sweeny took a look back at an intervention that upended the delicate balance between Iraq’s sectarian and ethnic groups, plunging the country into years of chaos and violence.