Historically Danzig has in the main passed through the same vicissitudes as West Prussia, of which it is the capital. It is an old Polish city, transformed into a German-speaking one since the fourteenth century. Nevertheless, German Danzig distinguished itself in the past by its loyalty to Poland. It took the lead and fought gallantly to effect the reunion of West Prussia with Poland in the fifteenth century. During the ensuing period of Polish rule, it was prosperous and contented. The whole sea-borne trade of Poland passed through its hands; it ranked as wellnigh the first port of the Baltic; and the wide measure of autonomy which Poland allowed it drew Danzig to her by affection as well as by interest. It was not without staunch resistance that the city surrendered to the Prussian usurpation in 1793, and as late as 1813 the City Council besought the Powers of Europe to reunite Danzig to Poland and not to incorporate it with Prussia. Today the problem of Danzig revolves around two essential facts. The city itself with a population of about 170,000, is overwhelmingly German (over 90%), and so is the small district immediately surrounding it.[47] On the other hand, economically and geographically, Danzig belongs to Poland. The city derives its importance almost wholly from the fact that it is the natural port of the Vistula valley: it is to that river what Marseilles is to the Rhone or Alexandria to the Nile.[48] Supremely prosperous during the best days of its union with Poland, Danzig has decayed and stagnated under Prussian rule. It has sunk to be a third-rate port, far outdistanced by Hamburg, Bremen, Stettin, or even Königsberg. It is doubtful whether it would have any future at all, if it were left as a German city, almost surrounded by Polish territory and cut off by political and economic barriers from the hinterland on which its life depends. For Poland this is almost the most crucial of all questions. Poland is essentially the valley of the Vistula. That river has always been the main artery of the country’s economic life, and scarcely any other European nation has its settlements concentrated in one river valley in like degree. The Vistula is a magnificent river system, a basin of 60,000 square miles with 3100 miles of navigable streams, and a possibility of opening good and easy connections with the Dnieper, the Dniester, and the Niemen--i.e., with half of eastern Europe. But the utilization and proper development of this unique system of transcontinental waterways by Poland depends on her control of the great port at the mouth of the Vistula. Moreover, Danzig is not only the natural outlet to the sea for this whole country, but it is the only outlet that is in any sense available. The narrow strip of coast which Poland has received to the west of Danzig contains no real ports, and it is doubtful whether any satisfactory port can be developed there.