Oppression always fails in the long run because the conditions that spawn the oppression always eventually pass, and oppressive regime has to keep justifying itself.<p>For instance, slavery was long on the way out of the US by the time of the Civil War. As we kept expanding west-ward, the new states had exactly zero economic incentive to turn people into livestock. The South could get away with political shenanigans only as long as it could maintain its voting bloc. Expansion made that impossible, and the only solution became a war.<p>If the war hadn't happened though, we would have seen a managed transition. Legislation tailored at reining in slavery would have slowly made the practice increasingly untenable and the economic aspect would have gotten managed out over time. In fact, it was already happening.<p>To generalize, oppression seeks out a local maximum, eventually society finds a higher peak, and the oppression only lasts as long as it takes for the rest of society to build a wide enough bridge so that people on the lower hill can just walk over to the bigger hill. Or, you know, a war.