During the Middle Ages, trade flourished between North Frisia and East Anglia, England. In particular, pottery was imported from the town of Ipswich and it has been suggested that relations between Frisians and East Anglians must have lasted for several centuries. In 1252, a united army of North Frisians from all territories between the Eiderstedt peninsula and the northern islands succeeded in defeating a Danish army led by king Abel. Salt making became a considerable trade in the 14th and 15th century when the North Frisians used saline peat as a resource. The salt trade coincided with an increase in international herring fishery off Heligoland. Treaties of 14th century farmers from Edoms Hundred with Hamburg based merchants and even the Counts of Flanders respectively have been preserved.