Krugman offers a really helpful analogy for the Greek crisis from Weimar Germany, which we always remember for the hyperinflation of 1923 when we ought to be thinking of the terrible deflation brought on by the austerity policies (cutting wages and welfare payments, tightening credit, and raising taxes) of Chancellor Heinrich Brüning in 1930-32, which was a decisive factor in bringing you-know-who into power in 1933. Austerity was a really bad idea for Germany, and has been a really bad idea for Greece so far.
An earlier and deeper cause of the collapse of the Weimar Republic, he goes on to note, was the terrible burden of debt imposed on Germany after the Great War by France and England under the terms of the Versailles Treaty in 1919, and the fruitless attempts of the Powers throughout the 1920s to collect this money (which they never came close to doing, even when French and Belgian troops occupied the Ruhr district in 1923-25 with the idea of taking it out directly in the form of coal).