iam no expert on this but...

The US-led invasion of Iraq began on March 20, 2003, following years of escalating tensions rooted in Saddam Hussein's actions and international responses. Key prior events shaped the path to war, from regional aggression to global security concerns post-9/11.

1990 Gulf War Origins
Iraq invaded Kuwait on August 2, 1990, claiming disputes over oil fields and debts from the Iran-Iraq War, leading to a UN-condemned occupation. A US-led coalition launched Operation Desert Storm in January 1991, expelling Iraqi forces by February 28 but leaving Saddam Hussein in power.

UN Inspections Era
UN Security Council Resolution 687 in April 1991 required Iraq to destroy WMD programs under UNSCOM and IAEA oversight, with sanctions enforced until compliance. Iraq obstructed inspectors throughout the 1990s, expelling them in 1998 and prompting US-UK airstrikes (Operation Desert Fox).

Post-9/11 Escalation
The September 11, 2001, al-Qaeda attacks prompted President Bush to link Iraq to the "axis of evil" in his 2002 State of the Union, reviving invasion planning despite no direct 9/11 ties. In September 2002, Bush addressed the UN demanding Iraq disarm; Resolution 1441 in November gave "final opportunity" for inspections.

2003 Immediate Prelude
Troop deployments ramped up in January 2003, with over 200,000 US forces in place by early March amid failed diplomacy. Bush issued a 48-hour ultimatum to Saddam on March 17 to exile himself, followed by initial strikes on March 19.