Operation Iraqi Freedom: The Biggest Consequence of the American Invasion of Iraq

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     In 2003, the United States invaded Iraq on the pretext of Iraq possessing weapons of mass destruction (WMD).  According to a radio address by former president George W. Bush, "Our cause is just, the security of the nations we serve and the peace of the world. And our mission is clear, to disarm Iraq of weapons of mass destruction, to end Saddam Hussein's support for terrorism, and to free the Iraqi people."

U.S. Solider perparees to take
the statue of Saddam Hussein.
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 What was estimated at first to be a very short and straight forward operation turned out to be a long and grueling process. Once the regime of Saddam Hussein was brought down (literally and symbolically), there was no state infrastructure left to hold Iraqi society together.

The Iraqi citizens, under threat, began to form militias to protect their own people. Iran had long wanted to see the fall of Saddam Hussein-- during the Iran-- Iraq war Ayatollah Khomeini originally refused to stop fighting until Hussein was removed from power. With Hussein out of the way, Iran was free to exert its influence on Iraq's Shi'a majority.
As a consequence of Iran exerting influence on the Shi'ites in Iraq and militias protecting their own sectarian violence skyrocketed. A series of maps shows the change of Baghdad over a few years from a largely mixed city to a predominantly Shi'a city:

The maps are color coded to show majority populations from 2003[top left], 2006 [top right], 2007[bottom left], and 2008 [bottom right].
Green= Shi'a Majority   Red= Sunni Majority  Blue= Christian Majority and Orange= Mixed
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A Sunni newspaper published the following political cartoon: Translations and image provided by BBC Middle East

"The cartoon depicts the map of Iraq as a pool of fuel leaked from a barrel with an Arabic phrase reading "Maliki's sectarianism" written on it. Then, a hand holding a lit torch seems to be trying to set fire to Iraq. On the sleeve, the word Iran is written, while the torch bears the name of the Iranian "al-Quds brigade".

Other evidence of rising sectarianism after the fall of Saddam Hussein includes the emergence of Sunni extremist group Da'ish (ISIS/ISIL/IS). Da'ish has been able to control a significant portion of Iraqi terrority. This would not have been possible before the U.S. invasion of Iraq.

Source: BBC