The new report by the Congressional Research Service estimates the U.S. has spent $648 billion on Iraq war operations, putting it in range with the $686 billion, in 2008 dollars, spent on the Vietnam War, the second most expensive war behind World War II. Since the Sept. 11, 2001, terrorist attacks, the U.S. has doled out almost $860 billion for military operations in Afghanistan, Iraq and elsewhere around the world.
All estimates, adjusted for inflation, are based on the costs of military operations and don't include expenses for veterans benefits, interest on war-related debts or assistance to war allies, according to the nonpartisan CRS.
The report underscores how the price tag has been gradually rising for the war in Iraq, which began in March 2003. In late 2002, then-White House budget director Mitch Daniels estimated the Iraq war would cost $50 billion to $60 billion. A year later, L. Paul Bremer, then-chief of the U.S. occupation government in Iraq, said the war would cost $100 billion.
Yet the Iraq war has consumed less of the nation's gross domestic product than other pricey conflicts. The Iraq war's costs represented 1 percent of GDP in the peak year of the war. World War II, with a $4.1 trillion price tag in 2008 dollars, was nearly 36 percent of GDP and the Vietnam War was 2.3 percent of GDP in that wars' peak years.
The report says comparisons of war expenses over hundreds of years "are inherently problematic" because of varying definitions of war costs. For example, the report's figures for the Vietnam War are Defense Department estimates of the incremental costs of military operations - the costs of war activities more than the normal, day-to-day costs of a standing military force. The costs for post 9/11 military operations are estimated from Congress-appropriated amounts and Defense Department reports.
The CRS report warns that comparisons of costs in inflation-adjusted prices are a "very rough exercise."
"It is difficult to know what it really means to compare costs of the American Revolution to costs of military operations in Iraq when, 230 years ago, the most sophisticated weaponry was a 36-gun frigate that is hardly comparable to a modern $3.5 billion destroyer," researchers wrote.
Here are the report's estimated costs of major wars, in 2008 dollars, and their costs as a percentage of GDP in each of their peak years: