A new analysis finds that due to the combined effects of capped topline budgets and internal cost growth inside the Pentagon, within the next 10 years, the vast majority of DoD’s budget will be swallowed up by just two budget categories: military personnel and operations and maintenance.

The projections, from the Center for Strategic and Budgetary Assessments, show that given historical trends of cost growth in personnel spending and O&M, those two items will consume 86 percent of the allowed DoD budget by 2021, the year that the spending caps imposed by the 2011 Budget Control Act expire.

Todd Harrison, CSBA’s senior fellow in defense budget studies, said depending on what trajectory those trends in cost growth take, the projections could be even more dire. Over the last 10 years, military personnel and O&M costs have been growing faster than usual: 4.2 percent and 2.7 percent per year, respectively, for every active duty service member.

“To scare you a little more, if the growth rates stay at what they’ve been for the past decade, together, those two accounts will consume the entire defense budget by 2024. You’d have no money left for procurement, for research and development, military construction, for family housing, nothing. Currently, all those other accounts consume about 36 percent of the budget,” Harrison told reporters at a news briefing Friday. “So we’re not on a good path here. DoD’s got to address some of these major structural issues. They’ve got to bend these cost curves significantly.”

More flexibility in future budgets?

DoD could have more flexibility in its spending plans in future years than it does in 2013. Under the budget control act, there are firm top-line budget caps, but the punishing, indiscriminate, program-by-program cuts that are happening this year won’t take place as long as Congress passes budgets that fit within those caps

However, each of the 2014 budget blueprints approved by the House and Senate propose DoD funding levels well above the $475 billion cap for the year, presuming that lawmakers will agree to cut the deficit in other ways and remove the currently enacted limits entirely. The budget the White House will propose in the coming days will reportedly make the same presumption and will fund DoD at higher levels.

Harrison doesn’t believe that’s a wise bet.