The U.S. currently has more than 5,000 American forces in Iraq, under an agreement between the two countries. The U.S. pulled its troops out of Iraq in 2011 when combat operations there ended, but they went back in after IS began to take over large swaths of the country in 2014. The number of American forces in Iraq has remained small due to political sensitivities in the country, after years of what some Iraqis consider U.S. occupation during the war that began in 2003.