In 1990 Saddam ordered his army to invade Kuwait and seize power. The U.S. and UN saw this as a violation of Kuwait’s sovereignty. In 1991, after a brief UN approval process, the U.S. and its coalition sprang into action. After a short engagement, they successfully stopped the Iraqi army and pushed them back across the border into Iraq. This conflict was known as the Gulf War.

During and after the war, Arabs had admired Saddam as a leader who dared to defy and challenge western powers. This admiration would loosely united the Arab world in the stance Saddam took. Saddam was a Sunni Muslim ruling in a predominantly Shia Iraq. Although his party was greatly outnumbered, against all the odds, Saddam’s ruthless policies and behavior were said to keep a balance of peace between the two Islamic sects in the country.

Following the war, and the exposure of the weak Iraqi army, the empowered Shiites in southern Iraq started a rebellion against Saddam. After the embarrassingly quick defeat at the hands of the U.S. coalition, Saddam desperately wanted to regain his stature among the people of Iraq by any means necessary. He struck down hard on the rebellion in his typical murderous fashion, slaughtering thousands of Shiites suspected — or not — of opposing him. It was at this point that allegations of the use of chemical and biological weapons against his people started surfacing.

As a result, the UN placed economic sanctions on Iraq.

Most would argue that the 2001 al-Qaida attacks on the U.S. triggered the U.S. to oust Saddam from power once and for all — a job most would agree should have been accomplished during the Gulf War.

Here are the fundamental reasons that ultimately led to the 2003 U.S. invasion of Iraq.

9/11 and the 1991 Gulf War were key influences that put Saddam in the world’s crosshairs.

The Bush administration called it a “belated reckoning” that needed to happen. Up to this point, Saddam had invaded or attacked four neighboring countries in the recent past and was directly responsible for the deaths of tens of thousands of Iraqi people. Also, post-Gulf War, a defeated Saddam had resorted to the mass slaughter of Kurds and Shiites. Many of the leaders in D.C. wanted to right the mistake of having left Saddam in power. But the issue was all but forgotten until 9/11 brought a crashing reminder of the Iraq-based al-Qaida terrorism.

The threat of Weapons of Mass Destruction in the hands of a “mad man” fueled the cause of the U.S. even further.

With the prospect of WMDs in Iraq, and given the unpredictability of Saddam’s actions, the CIA claimed that the intelligence of the overall situation was a “slam dunk.” Eastern governments, as well as a collection of European intelligence agencies, backed the U.S. intelligence. Of course, as we know now, Iraq never fully developed WMDs. This would later become a “critical political mistake.”