Tuesday marks the 10th anniversary of the United States' invasion of Iraq. Former president George W. Bush justified the 2003 invasion on the grounds that then-Iraqi leader Saddam Hussein possessed weapons of mass destruction. That assertion proved to be incorrect, as did the administration's initial prediction of a brief conflict. The third-longest war in U.S. history has claimed the lives of at least 190,000 people -- including 4,488 U.S. service members and 134,000 Iraqi civilians -- and has cost more than $2 trillion, according to a new Brown University study. We look back at the Iraq invasion and discuss the legacy of the war.