Complex sentence: The Italians in autumn 1918 expanded their Protectorate to areas of northern Greece and western Macedonia, conquered from the Bulgarians and Ottomans, but in 1920 were forced to fight the Vlora war.
Split into simpler sentences: The Italians in autumn 1918 expanded their Protectorate to areas of northern Greece and western Macedonia, conquered from the Bulgarians and Ottomans. But in 1920 were forced to fight the Vlora war.