with wars. If you lose, you get exterminated.
Genocide is almost never the conclusion of a war. If genocide is involved war is mostly a pretext for the Powers That Be to able to start genocide. There was no extermination of Germans, Japanese or Italians at the end of WWII, nor was there at the end of WWI. German (and other) war mongerers had a good shot at exterminating all jews in Europe, but they did not wage a war against them. The genocide was possible because of the 'fog of war' that made it hard for moderate forces in and outside Germany to see what was going on, exactly, and - when they found out - had their hands full on with other business, i.e. fighting a war.
"Look! There! Evil!.. pure and simple, total evil from the Eighth Dimension!" -- Buckaroo Banzai