When Charles succeeded Philip the Fair only a portion of the Netherlands was subject to his sway.  With steady persistence he set himself to the task of bringing all the seventeen provinces under one sovereign.  In 1515 George of Saxe-Meissen sold to him his rights over Friesland.  Henry of Bavaria, who in opposition to his wishes had been elected Bishop of Utrecht, was compelled (1528) to cede to him the temporalities of the see, retaining the spiritual office only.  Charles thus added the Upper and Lower Sticht—­Utrecht and Overyssel—­to his dominions.  He made himself (1536) master of Groningen and Drente after a long and obstinate struggle with Charles of Gelderland, and seven years later he forced Charles’ successor, William of Juelich and Cleves, to renounce in his favour his claims to Gelderland and Zutphen.  During the reign of Charles V the States-General were summoned many times, chiefly for the purpose of voting subsidies, but it was only on special and solemn occasions, that the representatives of all the seventeen provinces were present, as for instance when Philip received their homage in 1549 and when Charles V announced his abdication in 1555.  The names of the seventeen provinces summoned on these occasions were Brabant, Limburg, Luxemburg, Gelderland, Flanders, Holland, Zeeland, Artois, Hainault, Namur, Lille with Douay and Orchies, Tournay and district, Mechlin, Friesland, Utrecht, Overyssel with Drente and Groningen.  The bishopric of Liege, though nominally independent, was under the strict control of the government at Brussels.  The relations of Charles’ Burgundian domains to the empire were a matter of no small moment, and he was able to regulate them in a manner satisfactory to himself.  Several times during his reign tentative attempts were made to define those relations, which were of a very loose kind.  The fact that the head of the house of Habsburg was himself emperor had not made him any less determined than the Burgundian sovereigns, his ancestors, to assert for his Netherland territories a virtual independence of imperial control or obligation.  The various states of which the Netherlands were composed were as much opposed as the central government at Brussels to any recognition of the claims of the empire; and both Margaret of Austria and Mary of Hungary ventured to refuse to send representatives to the imperial diets, even when requested to do so by the emperor.  At last in 1548, when all the Netherland provinces had been brought under the direct dominion or control of one sovereign prince, a convention was drawn up at the diet of Augsburg, chiefly by the exertions of the Regent Mary and her tried councillors Viglius and Granvelle, by which the unity of the Netherland territories was recognised and they were freed from imperial jurisdiction.  Nominally, they formed a circle of the empire,—­the Burgundian circle—­and representatives of the circle were supposed to appear at the diets and to bear a certain share of imperial taxation in return for the right to the protection of the empire against attacks by France.  As a matter of fact, no representatives were ever sent and no subsidy was paid, nor was the protection of the empire ever sought or given.