In the early Middle Ages the Mark of Brandenburg, the centre and chief province of the modern Prussian State, was an outlying offshoot of the mediaeval Holy Roman Empire of the German nation, surrounded by barbaric tribes, Slav and Teuton.

The chief Slav people were the Borussians, from which the name "Prussian" was a corruption.

The first outstanding historic fact concerning these Baltic lands is that a certain Adalbert, Bishop of Prague, at the end of the tenth century went north on a mission of enterprise for converting the Prussian heathen.

The neighbouring Christian prince, the Duke of Poland, who had presumably suffered much from incursions of these pagan Slavs, offered him every encouragement.

The adventure ended, however, before long in the death of Adalbert at the hands of these same pagan Slavs.
The first indication of the existence of a Mark of Brandenburg with its Markgraves is in the eleventh century.