Lines were drawn on the map with no regard to tribe, culture or language divisions.
This is what totally fucked everyone and everything.
That mess was caused by the British (our oldest and most dangerous enemy).
They did it on purpose, with cold, calculating maliciousness towards the people in that whole region.
They didn't want stable, solid, unified countries as that would get in the way of their empire and the west being able to pillage the less advanced countries for all their wealth while handing a few baubles to a rich,corrupt,brutal local dictator who would need their constant support and help to not get overthrown and executed.
This is not something new, it has been done since the Assyrians/Persians. The British empire did this all over the world.
Then when that was not enough they went further with moving populations around to purposely create persecuted minorities and local ethnic tension.
Like Tamils in Sri Lanka, Indians in Fiji, African Slaves in America, Native Americans vs. Colonials, and the list goes on.
Then thanks to the UN and the western powers forcing their own strange constructs of countries to stay in existence the problem is never fixed.
We however aren't much better in recent history, we have been busy trying to overthrow anyone that could keep a country stable and preferring chaos for our own ends.
