Complex sentence: Though his rule was not stable because of the First World War, Essad succeeded in controlling much of central Albania until 1916, when he left for Serbia and Greece to help them in their war against Austria-Hungary.
Split into simpler sentences: Though his rule was not stable because of the First World War. He also succeeded in controlling much of central Albania until 1916, when he left for Serbia and Greece to help them in their war against Austria-Hungary.