How far did the first Bulgarian empire extend during Simeon I’s reign?

During the reign of Simeon I (893–927), the First Bulgarian Empire reached the high point of its power and territorial extent as a major Balkan state.123

As a gifted military leader, Simeon expanded Bulgaria’s borders significantly through various campaigns. By the time of his death, he was the master of the northern Balkans, a territory that included the Serbian lands. Reflecting this dominance, he styled himself "Tsar of the Bulgars and Autocrat of the Greeks," though his persistent efforts to capture Constantinople ultimately left the country near exhaustion.12

While Simeon brought the empire to its acme, he was also forced to relinquish certain territories north of the Danube River to new invaders arriving from the Eurasian steppe.3