For the next two centuries the Bulgarian Empire expanded, partly at the expense of their southern neighbour, the Byzantine Empire. The Empire had its greatest extent in the early 10th century under Simeon the Great, who in 913 adopted the title Tsar (meaning "emperor", ultimately related to Latin Caesar). After his death, however, Bulgaria's power began to decline, and by the year 1018 the country was conquered and ruled by the Byzantines.
In 1185 Petar and his brother Ivan Asen successfully revolted against the Byzantines and formed the Second Bulgarian Empire. The Asen dynasty ruled for almost a century. Eventually the second empire was conquered by the emerging Ottoman Turkish Empire in the late 14th century.
Russia defeated the Ottomans in the Russo-Turkish War in 1878, and after almost 500 years of Ottoman rule Bulgaria regained independence. A monarchy was reintroduced, but then abolished in 1946.