Why did the US and a coalition of 30 other countries send troops into Iraq in 2003?

The U.S. and a coalition of 30 other countries invaded Iraq in 2003 primarily based on claims that Saddam Hussein possessed weapons of mass destruction (WMDs) and posed a threat to international security. The invasion was also justified by the desire to remove Hussein from power and promote democracy in the region. Additionally, concerns about Iraq's ties to terrorism were highlighted in the context of the post-9/11 security environment. However, the absence of WMDs after the invasion led to significant controversy and debate regarding the legitimacy of the war.