The Ascanian line continued till 1319, and was followed by a period of political anarchy and disturbance, until finally Friedrich, Count of Hohenzollern, acquired the electorate, and became known as the Elector Friedrich I.Meanwhile the Order of the Teutonic Knights, who earlier began their famous crusade against the Borussian heathens, had established themselves on the territories now known as East and West Prussia.

In spite of this fact and of the for long time dominant power of their Polish neighbours, the Hohenzollern rulers continued to acquire increased power and fresh territories.
At the Reformation Albrecht, a scion of the Hohenzollern family, who had been elected Grand Master of the Teutonic Order, adopted Protestantism and assumed the title of Duke of Prussia.

Finally, in 1609, the then Elector of Brandenburg, John Sigismund, through his marriage with Ann, daughter and heiress of Albrecht Friedrich, Duke of Prussia, came into possession of the whole of Prussia proper, together with other adjacent territories.

The Prussian lands suffered much through the Thirty Years' War during the reign of John Sigismund's successor, George Wilhelm.

But the latter's son, Friedrich Wilhelm, the so-called Great Elector, succeeded by his ability in repairing the ravages the war had made and raising the electorate immensely in political importance.