The ratio of debt held by the public to national income, or gross domestic product (GDP) is a good indicator in determining the cost of war to a nation's domestic economy.
The higher the debt-to-G.D.P. ratio, the more a government will struggle to service its outstanding liabilities.
Throughout the history of America, the most common cause of increases in the debt-to-G.D.P. ratio has been the expenses associated with military conflict.
The nation's Congress, specifically the US, should routinely ask the CBO (Congressional Budget Office) to provide cost forecasts for potential future conflicts. These forecasts should account for all macroeconomic impacts of war spending on the domestic economy and on government debt.
Financing the wars through debt requires interest payments. The US paid about $200 billion in interest on war spending during the first decade of the wars. If war spending continues as forecast by the CBO, the country can expect to have paid about $1 trillion in interest by 2020.
Stabilizing the debt-to-G.D.P. ratio requires that future budget deficits be smaller than they have been over the last few years.
For further reading, refer to Institute for Economics & Peace's research paper called ECONOMIC CONSEQUENCES of WAR on the U.S. ECONOMY which aims to highlight the various macroeconomic effects of government policies and spending on the U.S. economy over the last seventy years during major periods of conflict.