Complex sentence: The Ottomans were unhappy with the outcome of the Treaty of Sèvres, which allowed the Great War victors control over much of the former Ottoman lands, through the distribution of formerly Ottoman territory as League of Nations mandates.
Split into simpler sentences: The Ottomans were unhappy with the outcome of the Treaty of Sèvres. This treaty allowed the Great War victors control over much of the former Ottoman lands, through the distribution of formerly Ottoman territory as League of Nations mandates.