You've picked some of the most coherent nations to make your case - but they're absolutely the exception. Rule by minority ethnic group is the classic tactic of

You've picked some of the most coherent nations to make your case - but they're absolutely the exception. Rule by minority ethnic group is the classic tactic of the British empire - they did it all over the world, from Ireland to India. Part of the reason why it works is because you don't actually need pre-existing divisions to make it work. If you take a country (say germany) and start treating a minority group far better than the rest (say, east germans), it wouldn't matter how arbitrary the division is before minor cultural and social differences start to really matter. Even something as 'small' as having government jobs open only to the minority group is usually enough to create massive divides in social and cultural norms. Part of the genius of the strategy is because even if you see it happening, and don't believe in it, you have to play along. If you're the hypothetical 'east german', you have to support the dictator, because the dictator losing power would, at the very least, lose you your good position - and at the worst, could have you killed in a pogrom. The dictator and the minority group have a symbiotic relationship - the minority group give the dictator enough support to draw loyal officers, government officials, police and so on from. The minority group in turn get kickbacks and privileges.