US forces have at last withdrawn from cities and towns across Iraq, handing control to local forces more than six years after the invasion. Those Americans left in Iraq will now be mostly confined to their barracks, in what military folk rather tediously call an 'overwatch' role. Basically they're able to step in if something goes wrong, but from here on in, the Iraqis are largely on their own.
You might think that things have been relatively quiet in Iraq in the two years since the 'surge' of US troops went after the bad guys and stopped much of the violence. And you'd be right, relatively speaking. But in the last couple of weeks there's been a sudden increase in bombings in Baghdad and elsewhere, which have left dozens of civilians dead. The people carrying out the attacks are keen to let everyone in Iraq know that the US is not leaving in victory, but is being forced out by the continued unrest.
The big question now is - how many more bomb attacks will the US allow to happen before its forces are ordered out of the barracks and back into the cities? Military bosses will be telling President Obama that relatively small operations in particular neighbourhoods could root out those behind the recent attacks, and that US troops wouldn't need to leave their bases for long. But Mr Obama will also have to consider the politics of all this. The reason the troops are leaving now is because he made an explicit promise to do so during his campaign for the presidency. To appear to go back on that promise, even if only for a short time, would be a political blow for him, and would also beg the question of how many more times US forces would be called on to leave their barracks to carry out further missions. Mr Obama would prefer not to have to send them back into harm's way at all. But if the bombings continue, he may feel he has no choice.