There are many speculative ( and specious ) arguments as to the causes of the great hyperinflation in Germany after WWI;  the need for credit to remold the Weimar Republic from war to peacetime industrial production,  monumental reparations payments demanded by the Allied Powers,  international currency speculation,  shortages of goods,  disturbances in the balance of payments between prices of exports and internal commodity prices,  avoiding revolution and anarchy,  a grossly unbalanced budget,  foreigners,  Jews,  etc.,  etc.  Pick your own theory!

The basic scenario in Germany has been repeated many times since.  The government, in order to finance some undertaking ( in this case, a war ), simply floated loans instead of raising taxes to pay for it.  Optimists that they were they believed that they would win and pay up with loot from the losers.  Once they lost and were saddled with enormous reparations payments themselves, the newly ( and weakly ) formed Weimar government just could not get support to simply tax everyone for the needed revenue.  Taxes are unpopular to say the least, and often lead to people dumping tea crates into the ocean and starting revolutions.  Rather than face the crisis by submitting to the inevitable foreclosure on Kaiser Bill's dream, the ersatz bureaucrats of the new republic ( no doubt, spurred on by the remaining monarchists, and fearful of the upsurgent socialists) did that voodoo that they do so well.  They found someone to blame - the Allies { in particular, the French},  -  and started pushing paper.  Hundreds of paper mills and printers, and thousands of clerks and accountants were employed in creating, distributing, and tracking billions of worthless banknotes at the height of inflation in 1923.

The one unavoidable fact that stands out is that the Reichsbank ( with the approval of the government) was printing up money as if it were toilet paper.

A prime instigator of this misery was Karl Helfferich who was secretary of the treasury during the war years of 1915 and 1916.  A right-wing politician, theoretical economist, sometime vice-chancellor, and occasional Bank director; he used his great influence to start Germany on an inflationary spiral during WWI by continually lending out government funds at extremely low rates and funding the war through loans.  Helfferich continued to pound nails into Germany's coffin after the war by becoming the reactionary Nationalist Party's greatest advocate in politics.

Mathias Erzberger, the Weimar's new minister of finance in 1919, temporarily succeeded in stopping the collapse of the economy in 1920 and stabilizing the currency with strict tax reform and collection - only to fall prey to Helfferich's bombastic arrogance.  Fed up with Helfferich's annoying accusations, Erzberger filed a libel suit against him.  Public sentiment went against him and he lost, ruining his reputation in the process.  Erzberger resigned as finance minister and the inflationary spiral picked up where it left off after his policies were removed.  Not content with ruining the man who tried to save Germany, reactionary advocates attempted to assasinate him during the trial  -  a year later they succeeded on a second attempt.

Curiously, Helfferich reversed his policies later when the inflation was at its worst, and was instrumental in the development of the Rentenmark stabilization currency.  However, his new money was to be a commodity-based "rye mark".  No doubt issued by a committee of his industrial and landowner cronies.  I assume after the laughter died down they figured it was better than nothing.

At the beginning of WWI the Reichsbank suspended redeeming paper notes with gold.  During the war the state urged it's citizens to be patriotic and redeem their gold coin hoards for paper marks to help the cash strapped government.  At the beginning of WWI the 20 mark coin pictured below was equal to about US $4.76.  But after the war, no one had gold, only paper marks   - and the presses kept rolling.  The German mark in relation to the U.S. dollar went from 17,972 to the dollar in January, 1923 to an incredible 4.2 billion paper marks on November 20th, 1923, when the Reichsbank released it's highest official exchange rate.  ( For the uninitiated; the standard for the time is the term "billion"= 1 million millions, the term "trillion"= 1 million billions, so, 4,200,000,000,000 mark = $1 )