The 'German' Hansa, a formally loose league of over 200 mercantile cities in and around the Holy Roman Empire, with regional headquarters in Bruges (Netherlands), London, Nowgorod (Russian furs) and Bergen (Norwegian smoked fish), controlled much inter-European land and sea trade for centuries. Modern historians study it based on recent finds in Lübeck, the crucial city and main headquarters. Mayor Johann Wittenborg learned the business from his father and left a rare accounting book. It proved crucial to the story of his execution after the Hanse's failed 1361-62 war against the Danish king Waldemar, who threatened to destroy the Hansa's Ostsee trade successfully, only to be defeated in 1638 by the next Hansa leader.
—KGF Vissers