Since the late 1380s grave piracy by privateers, promoted by Albert of Sweden and Mecklenburg actually directed against Margaret I of Denmark, blocked seafaring to the herring supplies at the Scania Market, thus fish prices tripled in Prussia. The Saxon Hansa cities urged Prussia to intervene, but Conrad of Jungingen was more worried about a Danish victory. So only after the cities, led by Lübeck's burgomaster Hinrich Westhof, had liaised the Treaty of Skanör (1395), Albert's defeat manifested, so that Prussia finally sent out its ships, led by Danzig's city councillor Conrad Letzkau. Until 1400 the united Teutonic-Hanseatic flotilla then thoroughly cleared the Baltic Sea from pirates, the Victual Brothers, and even took the island of Gotland in 1398. Later that year, however, the Luxembourgs gave the region in pawn to the Teutonic Order despite prior arrangements with Poland, and the Order kept it until Brandenburg redeemed it again in 1454 and 1455, respectively, by the Treaties of Cölln and Mewe. Though the possession of this territory by the Order strengthened ties between the Order and their secular counterparts in northern Germany, it exacerbated the already hostile relationship between the Order and Polish–Lithuanian union.