The election of Gustav Eriksson as a regent made many Swedish nobles, who had so far stayed loyal to King Christian, switch sides. Some noblemen, still loyal to the king, chose to leave Sweden, while others were killed. As a result, the Swedish Privy Council lost old members who were replaced by supporters of Gustav Eriksson. Most fortified cities and castles were conquered by Gustav's rebels, but the strongholds with the best defences, including Stockholm, were still under Danish control. In 1522, after negotiations between Gustav Eriksson's people and Lübeck, the Hanseatic city joined the war against Denmark. The winter of 1523 saw the joint forces attack the Danish and Norwegian areas of Scania, Halland, Blekinge and Bohuslän. During this winter, Christian II was overthrown and replaced by Frederick I. The new king openly claimed the Swedish throne and had hopes Lübeck would abandon the Swedish rebels. The German city, preferring an independent Sweden to a strong Kalmar Union dominated by Denmark, took advantage of the situation and put pressure on the rebels. The city wanted privileges on future trade as well as guarantees regarding the loans they had granted the rebels. The Privy Council and Gustav Eriksson knew the support from Lübeck was absolutely crucial. As a response, the council decided to appoint Gustav Eriksson king.