there is almost never a need for a country to go into debt. Debt is useful for entities that have a life cycle. People go into debt when young to buy a home, and then pay it back as they age. Companies go into debt to buy capital, and then pay it back as they mature. But a country (should) never die. There is no reason to pay for tomorrow what can be paid for today. The only reason ever to go into debt is if you have a tremendous, one time expense, that is large in relation to current income. Buying a home or a factory qualifies. But countries almost never have single one time expenses that are large in proportion to GDP. Thus they should never go into debt. Even a highway should be an operating expense for a country. The only time a country should go into debt is during war.This observation can also be applied in reverse. If you know a state has debt, then either (a) it is in a war, or has just come out of a major war (5-10 years), or (b) it is irresponsible and poorly run.
Devin Finbarr makes an astute point about national debt: