The U.S. decision to invade Iraq a decade ago resulted in nearly half a million deaths among the local population, with American-led forces causing the most fatalities in the worst area of violence.

A survey of 1,960 Iraqi households conducted by American and international experts found that 461,000 Iraqis died from the beginning of the war in 2003 until the U.S. and its allies pulled out in 2011.

“We think it is roughly around half a million people dead. And that is likely a low estimate,” Amy Hagopian of the University of Washington in Seattle, co-author of the report and leader of an international research team that polled heads of households and siblings across Iraq, told National Geographic.

“People need to know the cost in human lives of the decision to go to war,” she added.

Hagopian and her colleagues estimated about 405,000 deaths were attributed to the war and occupation in Iraq from 2003 to 2011.

Another 56,000 deaths were caused as a result Iraqis fleeing their country.

The experts said more than 60% of the “excess deaths of men, women, and children reported from 2003 to 2011 were the direct result of shootings, bombings, airstrikes, or other violence,” National Geographic’s Dan Vergano wrote.

The remaining fatalities came about indirectly, such as from stress-related heart attacks, bad sanitation or hospital care compromised by the war.

“In a war situation, people can't leave their homes to get medical care,” said Hagopian. “When they do…they arrive at institutions overwhelmed with violent injuries. The water is compromised. Stress is elevated. The power is out. The distribution networks for medical supplies are compromised.”

Baghdad was labeled the epicenter of violent deaths during the war. Coalition forces were blamed for 35% of the killings, followed by militias at 32%. However coalition forces were responsible for most of the deaths of women. According to the report, “Gunshots were reported to cause 63% of violent deaths; car bombs, 12%; and other explosions, 9%.”

-Noel Brinkerhoff

To Learn More:

Half-Million Iraqis Died in the War, New Study Says (by Dan Vergano, National Geographic)

This Chart Shows that the Iraq War Was Worse than We Think (by Max Fisher, Washington Post)

Iraq Study Estimates War-Related Deaths at 461,000 (BBC News)

Mortality in Iraq Associated with the 2003–2011 War and Occupation: Findings from a National Cluster Sample Survey by the University Collaborative Iraq Mortality Study (by Amy Hagopian, Abraham D. Flaxman, Tim K. Takaro, Sahar A. Esa Al Shatari, Julie Rajaratnam, Stan Becker, Alison Levin-Rector, Lindsay Galway, Berq J. Hadi Al-Yasseri, William M. Weiss, Christopher J. Murray, Gilbert Burnham; PLOS Medicine)

Iraq War Killed 116,000 Civilians (by Noel Brinkerhoff, AllGov)