'Long-Term Implications of the Fiscal Year 2010 Defense Budget'
In CBO's estimation, carrying out the Department of Defense's (DoD's) 2009 plans for 2010 and beyond...would require defense resources averaging at least $573 billion annually (in 2010 dollars) from 2011 to 2028.
"The department's resource requirements to execute the same plans could be even greater."
...Including the unbudgeted costs increases the projection to an annual average of $632 billion through 2028, or 18 percent more than the regular funding requested for 2010. Some 35 percent of the total unbudgeted costs between 2013 and 2028 are associated with overseas contingency operations; in particular, the analysis includes the potential costs—about $20 billion per year—of deploying 30,000 troops to contingency operations from 2013 through 2028. The total costs of $670 billion at the endpoint in 2028 would approach the peak of the past three years (measured in 2010 dollars), which includes the height of operations in Iraq.
Read full at CBO's Directors Blog