The early history of the state now called Prussia is chiefly the record of a thrifty family—the Hohenzollerns. Since the year 1415, when the overlordship of the sandy tract lying between the middle Elbe and lower Oder and stretching across their banks was conferred upon him by the Emperor for cash down, Frederick of Hohenzollern and his descendants had remained lords of Brandenburg. From Nuremberg, where Frederick had been Burggrave, they had brought with them the vital energy and business ability of successful townsmen. So poor was their new estate that for many generations relaxation would have meant ruin. There was therefore no temptation to depart from that policy of adding field to field which is the natural law of the industrious countryman. Whether from native superiority or from greater need, the Hohenzollerns were usually a little wiser than their neighbours. With the aid of a family statute of 1473, which made primogeniture the rule of succession for Brandenburg, they avoided the consequences of that custom of equal inheritance which has been the bane of Germany. By careful watching of opportunities, by windfalls, by purchase, and by covenants for mutual succession on failure of heirs made with neighbours whose lines died out, the domain of the rulers of Brandenburg was in two centuries increased fourfold. When the Thirty Years’ War broke out and the modern history of Prussia began, the head of the Hohenzollern family, who had long since become one of the seven Electors of the Empire, held sway over an area almost as great as that of Ireland.