Actions taken during WW1 helped to promote ethnic unity and destabilise the region for the next century.
As Lawrence of Arabia encouraged the Bedouin tribes to fight against the Ottoman Empire, he tried to provoke nationalism in the ethnicities living in the Empire at the time, for example, Syrians and Arabs. He encouraged them to fight for their freedom and promised an independent nation for those minorities in the Empire.
The Sykes-Picot agreement destabilised the region and broke the promises made by Britain and France for an independent nation for the Arabs, Syrians, Bedouins etc. They split the Middle East in accordance to their colonial spheres of influence and occupied different parts of the Middle East, the borders created caused anger and outrage for some, eg Israel-Palestine.