The United States invaded Iraq 20 years ago in order to find alleged weapons of mass destruction that could cause mass destruction and to end Saddam Hussein’s dictatorship.

Has anything been found or changed since this invasion?

Here’s what we know.

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Why did the U.S. invade Iraq? USA Today reported that “former President George W. Bush and his administration wagered to the American public and the international community that Hussein was hiding weapons of mass destruction.”

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Were weapons of mass destruction found in Iraq? In the CIA’s final report they detailed that no weapons of mass destruction were found, according to NBC News.

“After more than 18 months, the WMD investigation and debriefing of the WMD-related detainees has been exhausted,” head of the Iraq Survey Group, Charles Duelfer, reportedly wrote in the final report. “As matters now stand, the WMD investigation has gone as far as feasible.”

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What did the U.S. learn from the invasion? NPR reported that one of the lessons learned from the invasion is that wars are difficult to plan out because they are unpredictable and cost a lot of money.

“They basically planned for a best-case scenario, where the Iraqi people would cooperate with the occupation, that Iraqi units would be available to help secure the country in the aftermath of conflict, and that the international community would step in to help reconstruct Iraq,” then-Defense Secretary Donald Rumsfeld said, in radio call-in program.

Massachusetts Institute of Technology further reported that despite the fact that the U.S. military is one of the strongest in the world, planning doesn’t always help due to the unpredictable nature of war.