[4][5] With the subsequent clearance of nearby Landsberg (Warthe) (now Gorzow),[3] Frankfurt served to protect the Swedish army's rear when Gustavus Adolphus of Sweden proceeded further into Central Germany.

[5] Swedish king Gustavus Adolphus started to intervene in the Thirty Years' War by supporting Stralsund against Wallenstein in 1628, and landed in Pomerania in June 1630.

Except for Magdeburg, which had allied with Sweden on 1 August, the German Protestant states distrusted Gustavus Adolphus and hesitated to enter an alliance.

[4][5] The success was in part due to internal quarrels in the defending force—mercenaries who had not been paid refused to fight without receiving their pay first.

[5] Scottish major general in Swedish service John Leslie was appointed governor of the town and gave orders to have its defenses strengthened and the thousands of bodies buried.