sentences:  The operation was one of the biggest military operations in Iraq since the U.S. invasion in 2003.In mid-October 2006, al-Qaeda announced the creation of Islamic state of Iraq (ISI), replacing the Mujahideen Shura Council (MSC) and its al-Qaeda in Iraq (AQI).From January to June 2007, as part of the "surge", an additional five U.S. brigades arrived in Iraq and were deployed throughout the Baghdad Belts in preparation for the upcoming operation.