Why is the year 681 considered the beginning of the Bulgarian state?

The year 681 is considered the beginning of the Bulgarian state because it marks the formal recognition of the First Bulgarian Empire by the Byzantine Empire through a treaty.12

Following the collapse of Great Bulgaria, the Bulgar leader Asparukh led his people across the Danube River into the region between the river and the Balkan Mountains. After Asparukh’s forces defeated the army of the Byzantine emperor Constantine IV, the Byzantines were compelled to acknowledge Bulgar control over this territory. This diplomatic recognition established the foundation for the Bulgarian state, which would go on to play a significant role in the history of the Balkan Peninsula.12