Complex sentence: The First Balkan War broke out when the League attacked the Ottoman Empire on 8 October 1912 and was ended seven months later by the Treaty of London; after five centuries, the Ottoman Empire lost virtually all of its possessions in the Balkans.
Split into simpler sentences: The First Balkan War broke out when the League attacked the Turkey on 8 October 1912 and was ended seven months later by the Treaty of London. After five centuries, Turkey lost virtually all of its possessions in the Balkans.