Hanseatic league- A former economic and defensive confederation of free towns in northern Germany and neighboring areas. Traditionally dated to a protective alliance formed by Lübeck and Hamburg in 1241, it reached the height of its power in the 1300s and held its last official assembly in 1669. I can see Iris Flavia jumping up and down as I believe that King Henry II (the Lion) started the league.
This, on economic bases set up organization, actually was performing until XVII century. In the middle ages such trading-political union was necessary to protect land against unexpected military assaults by the Vikings, as well from the potential piracy. North Germany towns due to this union fast become the dominant economic force in Baltic Sea region and Lübeck – trading center, which was joining Baltic and Scandinavian countries.