Around the 12th Century, German regionalism was very strong with the northern lowlands having their own distinct languages of Saxon and Frisian. Efforts by Imperial central government to unify provincial and legal frameworks, while attempting to impose Middle High German as the official language, failed.
The importance of towns within this regionalism, they were the focus and strength of the local communities with the power to effect terms of trade, rights, position.
It was therefore a fertile period for the emergence of urban leagues, and in 1241 the first formal alliance between Lübeck and Hamburg was strengthened when they agreed to jointly protect trade routes on sea and land. This was the first formation of what would become the Hanseatic League. This league would expand, fight, defend, trade and negotiate across the next 400 years until Europe no longer needed it. But its legacy can still be seen and found today.