During the occupation by the U.S. 101st Airborne Division in 2003, a 21,000-strong force under General David Petraeus, the U.S. forces made a civil peace with the local Sunni tribes. However, after its pullout, the CIA allied itself almost exclusively with the Kurds, and the U.S. had been seen as essentially another tribal ally of the Kurds, making conflict inevitable. While one battalion of the 25th Infantry Division were heading out of Mosul to Fallujah to help in the attack on the city, insurgents were, ironically, coming into the city from Fallujah where they were joined by foreign fighters from across the border.