The Lost Children of the Lidice Massacre

  It shows the huge gulf between totalitarian fanatics and democracies that the Nazis sought to proclaim internationally such behaviour.  It may have cowered open resistance inside Czechoslovakia as the article suggested but did a lot to remove any doubt in the western allies about what they were fighting for.  Also I've often seen it argued as being a major factor in the deportation of the substantial German minority in the country so it definitely backfired for them.