US troops are withdrawing from towns and cities in Iraq, six years after the invasion, having formally handed over security duties to new Iraqi forces.
A public holiday - National Sovereignty Day - has been declared. In Baghdad, a giant party was held to mark the eve of the changeover.
US-led combat operations are due to end by September 2010 with all troops gone from Iraq by the end of 2011.
They will still be embedded with Iraqi forces until they are completely withdrawn from Iraq next year.
Iraqi troops are on the alert for insurgent attacks during the handover.
The BBC reports a recent upsurge in violence has created fresh fears about security when the US forces leave.
It is six years since the invasion that toppled Saddam Hussein.