No sooner did the news reach the ears of the Duke of Brandenburg than his fears overcame him, and he wrote to Gustavus withdrawing from the treaty he had made, and saying that as Spandau had only been delivered to him in order that he might march to the relief of Magdeburg he was now bound in honour to restore it.
Gustavus at once ordered Spandau to be evacuated by his troops, and again marched with the army against Berlin, which he had but a few days before left.

Here he again dictated terms, which the duke was forced to agree to.
The Swedish army now marched to Old Brandenburg, thirty-four miles west of Berlin, and there remained for some time waiting until some expected reinforcements should reach it.
The place was extremely unhealthy, and great numbers died from malaria and fever, thirty of Munro's musketeers dying in a single week.

During this time the king was negotiating with the Elector of Saxony and the Landgrave of Hesse.

These were the two most powerful of the Protestant princes in that part of Germany, and Tilly resolved to reduce them to obedience before the army of Gustavus was in a position to move forward, for at present his force was too small to enable him to take the field against the united armies of Tilly and Pappenheim.
He first fell upon the Landgrave of Hesse, and laid Thuringen waste with fire and sword.

Frankenhausen was plundered and burned to the ground.
Erfurt saved itself from a similar fate by the payment of a large sum of money, and by engaging to supply great stores of provisions for the use of the Imperial army.