By the way, this is quite interesting! Most events of 20th century were related to ideology. But before that, in old times maybe only religious wars were close to this. Other wars and conflicts were good old attempts to conquer someone and/or to gain resources and power. But was there as much hatred as produced by ideology? E.g. during the napoleonic wars many people died but does someone hate France because of Napoleon? I guess not. Or take WW1, it was only 107 years ago. Surely a lot of people died. Does someone remember it with hatred? Only as a great tragedy I think.