Joshua Goldstein says it happens:
How will the USA ever pay it back? Historically, there is a way that countries pay huge war debts. They print too much of their currency and cause its value to fall, thereby letting themselves pay off debts with funny money instead of valuable money. This is a huge simplification but explains the core of what happens. My 1988 book Long Cycles showed that over five centuries recurrent spikes of inflation followed major wars. In the past decade U.S. wars have been far from major in historical terms, and the current quasi-recession holds down inflation for now, but over the coming years I consider inflation likely.
The Dish 