A government issuing fiat currency can create inflation by way of currency creation to close a budget deficit as opposed to taxing their population or borrowing the needed funds.

When deficits handled in this manner prove to be chronic or large, so too is the amount of currency created to maintain the status quo. If the increased supply of money is not matched by a corresponding increase in the creation of goods and services, hyperinflation ensues.

In a hyperinflationary period, money loses it's buying power. As citizens lose confidence in the currency as a medium of exchange, they rush out to purchase goods with their money before it loses more value. The decreased demand for money coupled with an increased demand for goods and services accelerates prices further. Citizens abandon the currency and opt for other alternatives (a foreign currency, barter, gold) and the value of the inflated currency becomes largely theoretical.

It's punishing to savers, but quite forgiving to debtors, as interest rates do not keep pace with the rate of inflation.

Rich agrees to lend Paul $100, in exchange for five annual payments of $22 for a total of $110 over five years. Paul takes his loan and buys a car. A hyperinflationary episode ensues promptly. A year later, a car is worth $10,000. Paul sells the car, repays his debt to Rich, all $110 easily and ahead of schedule, and has $9890 on hand towards the purchase of another vehicle. So long as Paul acts fast, that is. In one years time, a car may cost $100,000 or $1,000,000.

So if you are a government in debt following a war or a catastrophe, and you happen to issue a fiat currency, and the debt is denominated in said fiat currency... sorry savers.