As I understand it there were some horrifying atrocities in Belgium - mass executions of civilians as reprisals, for example - but they were exaggerated and fictionalised for propaganda purposes. And then after the war the balace went the other way and they were minimised, and dismissed almost entirely. The truth lay in between.

One imfortuinate result of that was that reports of actual atrocities carried out by the Germans in the Second World War were often at the time taken to be the same kind of propaganda.

Sadly, as has been made painfully clear, large scale atrocities as horrifying as those attributed to Radetzky's men have in fact taken place in our own time.