The national power reached its zenith under Simeon (893-927), a monarch distinguished in the arts of war and peace. In his reign, says Gibbon, "Bulgaria assumed a rank among the civilized powers of the earth." His dominions extended from the Black Sea to the Adriatic, and from the borders of Thessaly to the Save and the Carpathians. Having become the most powerful monarch in eastern Europe, Simeon assumed the style of "Emperor and Autocrat of all the Bulgars and Greeks" (tsar i samodrzhetz vsêm Blgarom i Grkom), a title which was recognized by Pope Formosus. During the latter years of his reign, which were spent in peace, his people made great progress in civilization, literature nourished, and Prêslav, according to contemporary chroniclers, rivalled Constantinople in magnificence. After the death of Simeon the Bulgarian power declined owing to internal dissensions; the land was distracted by the Bogomil heresy (see Bogomils), and a separate or western empire, including Albania and Macedonia, was founded at Ochrida by Shishman, a boyar from Trnovo. A notable event took place in 967, when the Russians, under Sviatoslav, made their first appearance in Bulgaria. The Bulgarian tsar, Boris II., with the aid of the emperor John Zimisces, expelled the invaders, but the Greeks took advantage of their victory to dethrone Boris, and the first Bulgarian empire thus came to an end after an existence of three centuries.
The empire at Ochrida, however, rose to considerable importance under Samuel, the son of Shishman (976-1014), who conquered the greater part of the Peninsula, and ruled from the Danube to the Morea. After a series of campaigns this redoubtable warrior was defeated at Bêlasitza by the emperor Basil II., surnamed Bulgaroktonos, who put out the eyes of 15,000 prisoners taken in the fight, and sent them into the camp of his adversary. The Bulgarian tsar was so overpowered by the spectacle that he died of grief. A few years later his dynasty finally disappeared, and for more than a century and a half (1018-1186) the Bulgarian race remained subject to the Byzantine emperors.
In 1186, after a general insurrection of Vlachs and Bulgars under the brothers Ivan and Peter Asên of Trnovo, who claimed descent from the dynasty of the Shishmanovtzi, the nation recovered its independence, and Ivan Asên assumed the title of "Tsar of the Bulgars and Greeks." The seat of the second, or "Bulgaro-Vlach" empire was at Trnovo, which the Bulgarians regard as the historic capital of their race. Kaloyan, the third of the Asên monarchs, extended his dominions to Belgrade, Nish and Skopïe (Uskub); he acknowledged the spiritual supremacy of the pope, and received the royal crown from a papal legate. The greatest of all Bulgarian rulers was Ivan Asên II. (1218-1241), a man of humane and enlightened character. After a series of victorious campaigns he established his sway over Albania, Epirus, Macedonia and Thrace, and governed his wide dominions with justice, wisdom and moderation. In his time the nation attained a prosperity hitherto unknown: commerce, the arts and literature flourished; Trnovo, the capital, was enlarged and embellished; and great numbers of churches and monasteries were founded or endowed. The dynasty of the Asêns became extinct in 1257, and a period of decadence began.
Two other dynasties, both of Kuman origin, followed - the Terterovtzi, who ruled at Trnovo, and the Shishmanovtzi, who founded an independent state at Vidin, but afterwards reigned in the national capital. Eventually, on the 28th June 1330, a day commemorated with sorrow in Bulgaria, Tsar Michael Shishman was defeated and slain by the Servians, under Stephen Urosh III., at the battle of Velbûzhd (Kiustendil). Bulgaria, though still retaining its native rulers, now became subject to Servia, and formed part of the short-lived empire of Stephen Dushan (1331-1355). The Servian hegemony vanished after the death of Dushan, and the Christian races of the Peninsula, distracted by the quarrels of their petty princes, fell an easy prey to the advancing might of the Moslem invader.