In the 1240s the Pope offered King Håkon IV of Norway the opportunity to conquer the peninsula of Sambia. However, following the personal acceptance of Christianity by Grand Duke Mindaugas of Lithuania, the Teutonic Knights and a group of crusaders from Lübeck moved into Sambia, founding unopposed a fort in 1252 recorded as "Memele castrum" (or "Memelburg", "Memel Castle"). The fort's construction was completed in 1253 and Memel was garrisoned with troops of the Teutonic Order, administered by Deutschmeister Eberhard von Seyne. Documents for its foundation were signed by Eberhard and Bishop Heinrich von Lützelburg of Courland on 29 July 1252 and 1 August 1252.