Between March 20, 2003, and December 18, 2011 the US began a war with Iraq because Saddam Hussein had the potential of making weapons of mass destruction and the fact that US felt vulnerable after 911.
The war started when Saddam Hussein refused to leave Iraq the US launched bombs at Iraq’s military bunker complex then airstrikes against government and military installments. In a few days, US soldiers were dispatched to Kuwait to attack Iraq from the south. The US and UK were resisted from the south from irregular groups from the Ba'ath party known as Saddam fedayeen which were Saddam’s political party. A Heavily armed paramilitary that was apart of Saddam's parties was deployed to defend the capital of Baghdad the US armed forces and the marine passed more populated the more fedayeen resistance forced the US to pause 60 miles from Baghdad. During the pause US aircraft took heavy damage from Saddam's parties but, one week later the US took control of the airport and eventually got to the heart of Baghdad.
The leaders of iraq went into hiding and in december 13 2003 saddam hussein was captured convicted of crimes against humanity and sentenced to death in 2006. After Saddam's death, lots of people from Iraq was heard cheering from the news of Saddam Hussein's execution. Saddam was executed from his crimes against humanity mainly because he massacred 142 people from the Shiite party. In 2011 the US departed from Iraq.
https://www.britannica.com/event/Iraq-War
https://www.britannica.com/topic/Fedayeen-Saddam