In the 10 years since U.S. troops went into Afghanistan to root out the al-Qaida leaders behind the Sept. 11, 2001, attacks, spending on the conflicts totaled $2.3 trillion to $2.7 trillion.

Those numbers will continue to soar when considering often overlooked costs such as long-term obligations to wounded veterans and projected war spending from 2012 through 2020.

The estimates do not include at least $1 trillion more in interest payments coming due and many billions more in expenses that cannot be counted, according to the study.

In human terms, 224,000 to 258,000 people have died directly from warfare, including 125,000 civilians in Iraq.