The Iraq and Afghanistan conflicts, taken together, will be the most expensive wars in US history – totaling somewhere between $4 to $6 trillion. This includes long-term medical care and disability compensation for service members, veterans and families, military replenishment and social and economic costs. The largest portion of that bill is yet to be paid. Since 2001, the US has expanded the quality, quantity, availability and eligibility of benefits for military personnel and veterans. This has led to unprecedented growth in the Department of Veterans Affairs and the Department of Defense budgets. These benefits will increase further over the next 40 years. Additional funds are committed to replacing large quantities of basic equipment used in the wars and to support ongoing diplomatic presence and military assistance in the Iraq and Afghanistan region. The large sums borrowed to finance operations in Iraq and Afghanistan will also impose substantial long-term debt servicing costs. As a consequence of these wartime spending choices, the United States will face constraints in funding investments in personnel and diplomacy, research and development and new military initiatives. The legacy of decisions taken during the Iraq and Afghanistan wars will dominate future federal budgets for decades to come.
Bilmes, Linda J. "The Financial Legacy of Iraq and Afghanistan: How Wartime Spending Decisions Will Constrain Future National Security Budgets." HKS Faculty Research Working Paper Series RWP13-006, March 2013.