When the war flared up again after the intervention of France in 1635, the military situation of the emperor became increasingly precarious. In 1638, 1643, and 1645, the city of Vienna was threatened by Swedish troops. After the devastating defeat at the Battle of Jankau on 6 March 1645, it became apparent that the emperor was practically defenseless. The Habsburgs could no longer win the war without the support of the Spanish allies. Due to domestic difficulties, financial and military Spanish support for Ferdinand was completely stopped in 1645. Without foreign military funds, the imperial troops were incapable of progressive operation, which weakened Ferdinand's position in negotiations.