American troops have left Iraq after more than two decades, ending a military presence that began with the 2003 invasion and cost about 4,500 US lives.

The withdrawal follows a 2024 agreement between Washington and Baghdad, implemented under the Trump administration. Iraq declared a two-day public holiday, calling the moment a historic restoration of sovereignty.

So what changes? Iraq now takes full responsibility for its security. The government had set September 30 as the deadline for Iran-aligned militias to disarm, but compliance has been minimal, raising fears the factions could expand their influence.

For the US, the relationship shifts from boots on the ground to bilateral cooperation: intelligence sharing, weapons programmes and military training. Washington retains significant influence without the burden of deployment.

For the region, the key question is the balance of power. Iran-backed groups may test their strength, while Iraq’s government tries to steer between Washington and Tehran. The next year will show whether sovereignty brings stability.