The real blow to the prestige of the League was, however, the departure of the herring-shoals from the Baltic to the coasts of Amsterdam. ‘The Hansa’ had concentrated its commercial interests in the Baltic, and when the Baltic failed her she found herself unable to compete with the Dutch and English traders, who were already masters of the North Sea. Other and more adventurous rivals were opening up trade routes along the African coast and across the Atlantic; but the Hanseatic League, with her rigid and limited conception of commercial interests, was like a nurse still holding by the hand children that should have been able to fend for themselves. Once the protection of her merchants, she had degenerated into a check on individual enterprise, and so, belonging to the spirit of the Middle Ages, with the Middle Ages passed away. [Sidenote: The Teutonic Knights] Another mediaeval institution, destined also to decline and finally vanish, was a close ally of the Hanseatic League, namely, the Order of Teutonic Knights. Transferred, as we have noticed,[40] on the fall of the Latin Empire in Asia Minor to the shores of the Baltic, the Order had there justified its existence by carrying on a perpetual war against the heathen Lithuanians and Prussians, building fortresses and planting colonies of German settlers, as Charlemagne and his Franks had set the example. While there still remained heathen to conquer the Knights were warmly encouraged by the Pope, and their battle-fields were a popular resort for the chivalry of nearly every country in Europe, competing in their claim with the camps of Valencia, Murcia, and Granada. Nearer home the Order found less favour. In Poland, for instance, that had at first welcomed the Knights as a bulwark against northern barbarism, the unpleasant knowledge gradually dawned that the crusaders, by securing the territory of Livonia, Curland, and Prussia, had cut her off from a lucrative sea-trade. Poland was the most easterly of those states that in mediaeval times owned a nominal allegiance to Holy Roman Emperors. She had received her Christianity from Rome, and was thus drawn into the network of western life--unlike Russia, or the kingdom of Rus as it was called, that was converted by missionaries from Constantinople, and whose princes and dukes were subject to Mongol overlords in Siberia from the middle of the thirteenth to the middle of the fifteenth century. The Poles were brave, intensely devoted to their race, persistent in their enmities, and in none more than in their dislike of the German Knights, whose military genius and discipline had so often thwarted their ambitions. Quarrels and wars were continuous, but the most mortal wound dealt by the Poles was the result not of a victory but of a marriage alliance.