"The American military withdrew at the end of last year after negotiations for an extended troop presence collapsed because the Iraqis would not agree to extend legal immunities to any remaining force. Once the Americans left, Iraq celebrated its sovereignty, even as military officials in both countries fretted about the deficiencies of Iraq’s military and sought ways to work together that would not require a public debate about immunities.
Iraq and the United States are negotiating an agreement that could result in the return of small units of American soldiers to Iraq on training missions. At the request of the Iraqi government, according to General Caslen, a unit of Army Special Operations soldiers was recently deployed to Iraq to advise on counterterrorism and help with intelligence."
In other words, the US military was forced out of Iraq by the Iraqi government and now the Obama administration is planning on sending new troops into the country.