The various orders of knights, whose avocation it was to enforce conformity to the demands of Catholicism by the vengeance of the sword, was an important part of the papal machinery. All who yielded not to this argument were threatened with extermination; all who did, became the slaves of spiritual despotism. Under pretext of protecting Poland from the ravages of Prussian heathen, the Teutonic Knights, in 1226, won from Conrad of Masovia a small strip of land on the Vistula. For fifty-three years they carried on a war against the Persian tribes, and finally obliged them to embrace Catholicism. This war, suggested by papal craft, continued by incredible barbarity, culminated in the grossest perfidy. In their protection of Poland they inflicted deeper injuries on her than the savages of Prussia had ever contemplated, or in fact had the ability to inflict. They subjugated the Baltic seaboard, from the Oder to the Gulf of Finland, and wrung from her her maritime commerce, and her northern line of defence. Poland and Prussia having both been plundered and oppressed by the knights, united in a bond of union against their common enemy, and a ferocious war was inaugurated, during which the knights lost a great portion of their territory, and finally their power was broken. In the various vicissitudes of the succeeding fifty years the knights became abolished in Prussia, and their possessions converted into a hereditary duchy, under the male line of Prince Albert, which, under Francis III. became the kingdom of Prussia.