The Iraq War began in March 2003 with an air campaign, which was immediately followed by a U.S.-led ground invasion. The Bush administration cited UNSC Resolution 1441, which warned of "serious consequences" for violations such as Iraq possessing weapons of mass destruction. The Bush administration also stated the Iraq war was part of the War on Terror, a claim later questioned and contested. Iraq had been listed as a State sponsor of terrorism by the U.S. since 1990, when Saddam Hussein invaded Kuwait.