Having secured the eastern front, the King was able to concentrate on the recovery of Baltic areas lost by his father to Sweden. Władysław IV wanted to take advantage of the Swedish defeat at Nördlingen and fight for both the territories and his Swedish dynastic claims. The Poles were suspicious of his designs and war preparations and the King was able to proceed with negotiations only, where his unwillingness to give up the dynastic claim weakened the Commonwealth's position. According to the Treaty of Stuhmsdorf of 1635 the Swedes evacuated Royal Prussia's cities and ports, which meant a return of the Crown's lower Vistula possessions, and stopped collecting custom duties there. Sweden retained most of Livonia, while the Rzeczpospolita kept Courland, which having assumed the servicing of Lithuania's Baltic trade entered a period of prosperity.