Iraq Warn. A protracted military conflict in Iraq that began in 2003 with an attack by a coalition of forces led by the United States and that resulted in the overthrow of Saddam Hussein’s regime. US combat troops were withdrawn in 2010.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.