In spite of all that has been written about the supposed affinities and desires of the population of Alsace-Lorraine, it must not be forgotten that the national interests of Germany and France are vitally concerned in its possession, not merely in the general sense of the desire to keep or to recover something which has been fought over as a matter of national honor, but in the very definite respects of military advantage and economic power. And there have been times when these considerations were put nakedly in the foreground as the dominant motives. Thus Emperor William I wrote to Empress Eugénie October 26, 1870: “The required cessions of territory have no other purpose than to set back the point of departure of the French armies which will come to attack us in the future.”[23] German blood, said Bismarck, “was shed not for the sake of Alsace-Lorraine, but for the German empire, its unity, and the protection of its frontiers.”[24] Stern treatment of its people he defended on the ground that it was the glacis of a fortress, to be used for the benefit of the Fatherland behind it, irrespective of the desires of the conquered.[25] The military purpose of the annexation was also evident from the boundaries of the ceded territory. The frontier of the Vosges, of obvious advantage to Germany from a strategic point of view, might also be argued for on other grounds as the natural line of demarcation between Alsace and France--the watershed between two river systems, in part the boundary between French and German speech, etc. No such ‘natural’ or linguistic argument, however, could be urged for the annexation of French Lorraine. Here the obvious and declared object was the fortress of Metz, dominating the approaches to the upper Rhine by way of the Saar and to the middle Rhine by way of the valley of the Moselle. Bismarck, it is generally understood, wished to take only Alsace and feared the danger of a French population in the west, but Moltke and the military party insisted on Metz and had their way. Still another consideration had weight in drawing the frontiers of 1871, namely the iron deposits of Lorraine. Apart from the potash of Upper Alsace, it so happens that the great natural resources of Alsace-Lorraine lay on its outer edges, in the coal of the Saar valley and the iron of the Lorraine border. The problems of the Saar will be discussed in the next chapter in relation to the frontier of 1814; those of the Lorraine frontier are particularly instructive in connection with our present subject.