Although this doesn't mean the war is going to end really quickly, it is an important stage in bringing fighting to an end.
America is also going to be withdrawing two of its three aircraft carriers from the Gulf this week.
In cities that are already under control, the US military has promised to bring back law and order.
There's been widespread looting in many places, but this is gradually stopping.
More than 2,000 Iraqi policemen are said to have returned to work after the US appealed for them to come back and help the situation.