After 2003, more and more Iraqis began to see the U.S. as an occupying force. The fierce fighting of the First Battle of Fallujah alienated many in Iraq, while cleric Muqtada al-Sadr encouraged Shia Muslims to oppose the CPA. Sunni and Shia insurgents engaged in a campaign of guerrilla warfare against the United States, blunting the technological and organizational advantages of the U.S. military. While fighting in Iraq continued, Americans increasingly came to disapprove of Bush's handling of the Iraq War, contributing to a decline in Bush's approval ratings.