For the area around the Baltic Sea the century between 1150 and 1250 was a time of changes. Socially old structures were dislocated by the "invention" of the German town and economically the ways of transit changed from the Scandinavian north to the German south of the Baltic Sea. In the traditional research this phenomenon was connected to two main factors: the foundation of the city of Lübeck in 1158/59 and the German invention of the cog, the alleged most modern type of ship with the highest loading capacity. Both explanatory models are wrong. Neither was the city of Lübeck a new foundation in 1158 and was from the beginning not conceived as a transit harbour between the Baltic and the North Sea nor was the cog just as little a pure German invention as the type of ship with the highest loading capacity as the latest archaeological excavations have shown. So we have to look for other models to explain these most significant changes in the Baltic Sea area.

In my paper I will develop an explanatory concept which shall consider four main factors behind the changes at this time: 1. The economical changes in central and northern Europe or more especially, which kind of merchandise was demanded in both areas, 2. which merchants took part at that trade and in which way, 3. which legal certainty they had and by which ways they tried to advance their position and 4. which means of transport were available in the harbours of the Baltic and by whom they were belonged.

I want to show, that the changes around 1250 were the suddenly visible result of a long process. The merchants form the German inlands came to the Baltic around 1100, first they participated in the existing systems of trade, were later able to change the system effectively and least were able to align the whole after their own requirements. The "foundations" of "German" towns were only one result of this process as the intensified use of the cog, a type of ship with worse sailing qualities but with the lowest costs of manufacture. The changes in the urban landscape, in the social structure of the merchants and the increasing use of unesthetic but cheap ships are the logical result of this development not the activator.

By the end I hope to give a more historical than nationalistic view on the changes in the flow of trade around 1200. The system which arose at this time was so modern, that it lasted for the next 700 years.