After WW I, one of the largest and bloodiest wars the world has seen, Germany was forced to sign the War-Guilt clause at the Treaty of Versailles. This declared that Germany and its allies held complete responsibility for all “loss and damages” suffered by the Allies during the war. The old imperial system was dissolved and a new republic called Weimar was established.
By signing this clause Germany was forced to provide the basis for reparations, which was 132 billion gold marks. This was more than their entire reserves in gold and foreign exchange. The result of this was that the government was forced to print more and more money to pay for the bills. This spiraled their economy out of control, and they suffered what's known as hyperinflation. Hyperinflation was so bad that there are reports that kids used bricks of bills as toys. The money was that worthless, because they had printed so much for it.
This amount was so extreme at the time that it was even more than the total German gold or foreign exchange. Citizens felt the massive burden of the reparation payments felt like they forced upon Germany and are often cited as a major basis for the rise of Hitler and WWII. They were certainly huge, if they were still paying until 2010!