During medieval times, Büsum was frequently visited by traders of the Hanseatic League. The Hansa was the main ally of Dithmarschen, but the peasants' republic never became part of the Hanseatic League itself. The people of the comparatively poor island Büsum often resorted to piracy to better their lives, resulting in repeated conflicts. In 1420, Rackler Kersten and his men from Büsum sailed into the harbor of Hamburg to scuttle and loot Hanseatic trading ships. In retaliation, the Hamburgers pillaged and burned the island's church in Middeldorp. The new church was built in Norddorp and furnished with several items looted from the island Pellworm by the pirate Cord Widderich.