Europe's history is full of this, but yes no joke there were many, many political observers who, not too long after the conflicts in the Balkan countries in the late 90s, and as countries formerly under Soviet influence became liberal democracies felt that this era of European history was in the past, that liberal democracies wouldn't invade one another yada yada and that there would never be any more wars in Europe.

Obviously they were wrong, or perhaps there just needed to be an asterisk next to Russia as they quickly regressed away from becoming a liberal democracy and all the conflicts recently have involved Russian aggression against its neighbours.