High Quality Content by WIKIPEDIA articles! Most of Greece was part of the Ottoman Empire from the 15th century until its declaration of independence in 1821, a historical period also known as Tourkokratia (Greek: , "Turkish rule"). The Byzantine Empire, which had ruled most of the Greek-speaking world for over 1100 years, had been fatally weakened since the sacking of Constantinople by the Crusaders in 1204. The Ottoman advance into Greece was preceded by victory over the Serbs to its north. First the Ottomans won at 1371 on the Maritsa River where the Serb forces were led by the King Vukasin Mrnjavcevic, the father of Marko Kraljevic and the co-ruler of the last emperor from the Serbian Nemanjic dynasty. This was followed by another Ottoman victory in the 1389 Battle of Kosovo.