The Iraq War (2003-2011), also known as the Second Gulf War, was a prolonged armed conflict in Iraq that began with a U.S.-led coalition invasion, primarily involving troops from the United States and the United Kingdom. The invasion was justified by claims of Iraqi possession of weapons of mass destruction (WMD) and links to terrorism as part of the broader Global War on Terror. No WMD were found, leading to significant controversy. The war resulted in the overthrow of the Ba'athist government under Saddam Hussein and evolved into a violent insurgency against coalition forces and the new Iraqi government. U.S. forces were officially withdrawn in 2011. In 2014, the U.S. re-engaged in Iraq leading a coalition under Operation Inherent Resolve to combat the Islamic State (ISIS) insurgency.