The Teutonic Knights conquered Prussia, Livonia, and Courland, and in 1283 became masters of the whole territory between the Vistula and the Niemen. In 1309 they abandoned Venice, where, twenty years earlier, their grand master had fixed his ordinary residence, and selected Marienburg as their head-quarters. At that date the order had reached the culminating point of its prosperity, and its sway in Germany had the most fortunate results for Prussia. But luxury soon began to undermine the religious faith of the knights; and internal struggles, caused by the elections of their grand masters, introduced fresh elements of decay into their organization. [Illustration: Fig. 153.--Sancha de Roxas, who died in 1437, wearing the scarf which was the insignia of the military order bearing his name (Fifteenth Century).--From the “Iconografia Española” of M. Carderera.] Dragged into endless conflicts with Lithuania and Poland, the order lost its banners, its treasure, and its principal defenders in the disastrous battle of Grümwald, in the year 1410, and would have been utterly ruined but for Henry von Plauen. After the death of this illustrious grand master, the knights, to whom the treaty of Thorn had restored their territorial possessions, lost them one after the other in the few years that elapsed between 1422 and 1436. For thirteen years Casimir IV., King of Poland, summoned into Prussia by the inhabitants, who had rebelled against the despotic sway of the knights, laid waste the country that he had undertaken to protect. The order, driven out of Marienburg and Konitz, only retained possession of Eastern Prussia, and held even that under Polish rule; its grand master, whose head-quarters were now at Königsberg, was, in fact, a prince and a councillor of Poland. As Prussia was a fief of the Church, the grand master of the Teutonic Order was bound by vow to preserve it to the Church and to his own order. Albert of Brandenburg, its last grand master, was bound by this oath, and by the triple vow of poverty, obedience, and chastity, which he had taken on entering the order. To rid himself of the fetters of these oaths he joined the Lutheran Church, and divided the possessions of his order with his uncle, the aged Sigismund, King of Poland, who for these considerations bestowed on him the title of hereditary Duke of Prussia. This was the origin of the royal family of Prussia. After this easy acquisition of title and territory, Albert of Brandenburg married the daughter of the King of Denmark. As a matter of course, the Order of the Teutonic Knights became extinct. [Illustration: Fig. 154.--Teutonic Knight.--Fac-simile of a Woodcut by Jost Amman, in his work entitled “Cleri totius Romanæ ecclesiæ ... habitus:” 4to, Frankfort, 1585.] [Illustration: Fig. 155.--Chapter of the Golden Fleece, held by Charles the Bold.--Manuscript of the Fifteenth Century, in the Burgundian Library, Brussels.]