However censurable the means by which Birger arrived at power, he had qualities worthy of the post. He founded Stockholm, which he also fortified: he revised and greatly improved the Landslag, or written laws of the kingdom; he conferred on the cities and towns privileges similar to those contained in the charters of later ages; he improved the internal administration in other respects; while he defended the coasts against the ravages of the pirates. Such indeed was the prosperity which he introduced, that the diet requested the king to confer on him the ducal title—a title previously unknown in Sweden. But the success of his administration, and the power held by his family, incurred first the jealousy, and soon the hatred of a faction, or rather of several factions who united to oppose him. Among the great Swedish families was one that rivalled the Folkungar in riches, in the number of its armed dependents, in its widely-spread connection. This was the Folkungar family, which had beheld with the deepest mortification the elevation of a rival house. A civil war followed, which was indecisive; and it was ended by a pacification, but a pacification dictated by deceit. After Birger had solemnly sworn to it, and the heads of the other party repaired in unsuspecting confidence to his camp, he caused them to be put to death. One noble only escaped, Charles, who fled to the Teutonic knights, became a member of the order, and left an heroic name behind him. This perfidious act is a sad stain on the glory of his regency. Another was his excessive love of power, which induced him to retain the reins of government long after his son had arrived at manhood, and even after that son had married Sophia, daughter of Eric Plough-penny, king of Denmark. Death only caused him to release his grasp. [Sidenote: 1266 to 1276.]