The main cause of the Iraq War in 2003 was the belief that Iraq possessed weapons of mass destruction (WMDs) that posed a threat to international security. The U.S. government, led by President George W. Bush, argued that Iraqi President Saddam Hussein was defying United Nations resolutions and could potentially use WMDs against the U.S. or its allies. Additionally, there were concerns about Iraq's ties to terrorist organizations following the September 11 attacks in 2001. Despite extensive military action and a subsequent occupation, no HMDs were found, leading to widespread criticism and debates about the legitimacy and consequences of the invasion.