Economics experts here can hopefully help me out here!
This is sort of a generic question, based in a 1900 to 1925ish timeframe. What would happen economically if a non-Russian Great Power in Europe were to experience a revolutionary change in Government? Here's the catch: while Germany in OTL would seem to provide a good example of the economic dislocation, I'm wondering about a nation that wasn't at war with the countries it owed money to.
In summation: a far left government takes power in a Great Power that owes money to non-far left Great Powers. This far left government is neutral to the countries it owes money to at best; what steps could it take to remedy these awkward loans to capitalist states? Could it simply say "You're not getting this money back, ever?" That would have serious ramifications, I suspect. Is there something similarly heavy-handed that it could do that wasn't quite as drastic?