A 2023 update to the original 2021 report from Brown University’s Costs of War Project has revealed the staggering human and financial toll of the United States’ post-9/11 military campaigns, estimating at least 4.5 to 4.7 million deaths across multiple war zones and $8 trillion in costs.

The study, released by researchers at the Watson Institute for International and Public Affairs, found that between 897,000 and 929,000 people were killed directly by war violence in Afghanistan, Pakistan, Iraq, Syria, Yemen, and other affected regions. Far higher, however, are the estimated 3.6 to 3.8 million indirect deaths caused by war-related destruction of healthcare systems, food supplies, infrastructure, and the environment. Researchers noted that children represent a significant share of these casualties due to the spread of disease and lack of medical care.

“The deaths we tallied are likely a vast undercount of the true toll these wars have taken on human life,” said Neta Crawford, a co-founder of the project and professor of political science at Boston University.

The financial burden is equally striking. Since 2001, U.S. wars have cost roughly $8 trillion, including $2.3 trillion in the Afghanistan-Pakistan theater and $2.1 trillion for Iraq and Syria. The figure also covers homeland security spending, interest payments on war borrowing, and future veterans’ care, which alone is projected to reach $2.2 to $2.5 trillion by 2050.

Beyond deaths and costs, the report documents widespread displacement, estimating 38 million people have been forced from their homes. It also highlights systemic issues within the U.S. military, noting that 24% of women service members and 1.9% of men reported experiencing sexual assault during the Afghanistan war.

Researchers also connected U.S. wars to global environmental damage, pointing to the Department of Defense as one of the world’s largest greenhouse gas emitters. They further warned that militarization extends beyond the battlefield, with American culture, media, and politics increasingly shaped by what President Dwight Eisenhower once called the “military-industrial complex.”

“The Pentagon and the U.S. military have now absorbed the great majority of the federal discretionary budget, and most people don’t know that,” said Catherine Lutz, co-director of the Costs of War Project.

The figures and statistics were calculated prior to October 7, 2023, meaning they do not reflect the additional casualties and costs of the U.S.-backed Israeli genocide in Gaza and related regional operations.

“What have we truly accomplished in 20 years of post-9/11 wars and at what price?” asked Stephanie Savell, co-director of the project. “Twenty years from now, we’ll still be reckoning with the high societal costs — long after U.S. forces are gone.”