The first of these plebiscite areas is the Marienwerder district on the right bank of the Vistula in the northeastern corner of West Prussia. This small territory is of much importance to Poland, since it borders upon the Vistula and, if left in German hands, might menace the security of communications along that river. Moreover, the most direct and convenient railway from Danzig to Warsaw runs across this territory. Nevertheless, since the district contained in 1910 about 114,000 Germans as against only 24,000 Poles, the Conference decided to refer its fate to a plebiscite. Apart from Danzig, this is the only considerable district with a German-speaking majority which may be taken away from Germany. A plebiscite is also to be held in the southern zone of the province of East Prussia, in the territory commonly known as Mazuria. This secluded region of forests, lakes, and marshes has a decided majority of Polish-speaking population. The ancestors of these Poles were called into the country in the thirteenth and fourteenth centuries by the Teutonic Knights to replace the original Prussian population, which the Knights had largely exterminated. The Mazurian Poles have remained politically separated from the rest of their nation for six hundred years; since the sixteenth century they have become Protestants, while almost all the other Poles are Catholics; and because of these facts and also because of their economic, intellectual, and spiritual dependence on their German landlords, teachers, and pastors, the Mazurian Poles have long been completely estranged from the rest of the Polish nation. They have on the whole shown no very marked signs of Polish national consciousness, and there was room to doubt whether they desired reunion with Poland. Hence, a plebiscite was clearly in order here.