The Jesuits circulated the report that the king of Sweden had voluntarily left Magdeburg to perish. They hoped by that means to alienate the other Protestants from Gustavus. It was not difficult for him to clear himself of this charge, and most histories now agree that the destruction of Magdeburg was due to the prejudices, envies, jealousies and mistrust of the Electors of Saxony and Brandenburg. Gustavus had written the Elector of Saxony, when Magdeburg was threatened: "I see myself obliged to lower my pretensions and not to advance further. To post myself between two wavering powers, or to abandon the rivers by which all my convoys arrive, would be contrary to all rules of military science. However, I wish to show Magdeburg how much solicitude I feel for her, and should I sacrifice my life, I shall do all I can to deliver her. May God sustain me by His grace, and make my perseverance triumphant. Before God and before men I declare that I am innocent of all the blood that will be shed, and of all the misfortunes that will happen."
The terror and agony caused by the destruction of Magdeburg soon changed to hot indignation, and the German people raised such a hue and cry against their princes that they were, for the most part, glad to throw themselves into the arms of the king of Sweden. But that hopeful brother-in-law refused even to permit Gustavus to hold the fortress of Spandau.
Gustavus well knew that if he left Brandenburg, Berlin would follow Magdeburg, so, as he retreated from Spandau, either as a huge joke or in earnest, he planted his artillery to command the city of Berlin. The ladies of the Elector's family came in person to entreat Gustavus not to move north and leave them to the mercy of the Imperialists, and to beg him not to shell the city. They assured him that the Elector would treat with him, make any treaty—only Gustavus must not leave the Duchy to the fate of Magdeburg. Munro says: "And the king answered, merrily, that if the Duke did not conclude a treaty with him before night he would send the Duchess and all the ladies prisoners to Sweden, and that the Duke should follow." The alliance was concluded June 11th, Gustavus to hold Spandau during the war, and to have free passage through Kustrin and to use any other fortresses he might need. A payment of thirty thousand dollars a month and liberal contributions for the support of the army were also granted.
About this time Gustavus learned that Greifswald, the only fortress which the Imperialists yet held in Pomerania, had surrendered to the Swedish General Ake Tott. The Czar of Moscow sent messengers to congratulate him, also to renew his alliance and to offer him troops. Gustavus was much gratified at this attitude of Russia, as it was most desirable to keep Sweden undisturbed by any foreign foe while its king was absent from his country.
The latter part of June Gustavus employed in reinstating the Dukes of Mecklenburg, who were now put into full possession of all their duchy, except Rostock and Wismar. They proved very ungrateful, and General Ake Tott had great difficulty in making them furnish their share of contributions for the war which gave back to them their possessions.
General Tilly now marched direct from Magdeburg to Thuringia, in order to force the Landgrave of Hesse to disband the troops he had gathered for the assistance of the king of Sweden, also to force him to receive Imperial garrisons in his fortresses, and to pay a large war indemnity. Of course, he refused to comply with these demands. As Tilly passed over the country everything was laid waste. His army had been almost as demoralized by the victory at Magdeburg as if it had been a defeat. The men of the army seem never to have desisted even for a single day from robbery, arson and all forms of nameless crimes.
Meanwhile, General Bauer, of Gustavus' army, had stormed Havelberg, so that now the Swedes held nearly all the country north of the Elbe, and were ready to take the aggressive. But think of it, he had been obliged to conquer the duchies of Mecklenburg and Brandenburg, whose princes were Protestants and should have been more interested in bringing the army supplies, furnishing troops and driving back the Imperialists, than Gustavus himself. It was not their religion, but their lack of religion that was at fault.
The Landgrave of Hesse gave Tilly's troops such a severe rebuff that the Imperial army was ordered immediately into Thuringia, but Tilly, hearing where Gustavus and his army were located, made his way to that portion of the country and encamped on the same side of the Elbe River as Gustavus.
The Swedes routed three of Tilly's regiments, carried off most of their baggage and burned the remainder. But Gustavus' army had been weakened by much sickness during the winter and he carefully avoided a general engagement, while Tilly considered the entrenchments of the Swedes far too formidable for assault. Tilly wasted considerable time before the Swedish camp, then bent his course toward Saxony. Up to this time this country had been spared, because of the loyalty of its ruling house to Austria, and because Emperor Ferdinand II. earnestly desired to keep Duke John George with his party, but it was a rich country, and now Tilly and his hordes pounced upon it like birds of prey on a carcass. A line of two hundred burning villages marked Tilly's march to the neighborhood of Leipzig.
Now the Elector, when the beak of the enemy was at his own vitals, turned quickly to Gustavus. He sent Field Marshal Arnheim to request the immediate help of the king of Sweden. The king must have been gratified, though no word of history shows any exultation on his part. He replied to the Field Marshal: "I am sorry for the Elector; had he heeded my repeated remonstrances his country would never have seen the face of an enemy, and Magdeburg would not have been destroyed. Now, when necessity leaves no other alternative, he seeks my assistance. But tell him that I cannot, for his sake, ruin my own cause and that of my confederates. What pledge have I for the sincerity of a prince whose minister is in the pay of Austria and who will abandon me as soon as the Emperor flatters him and withdraws his troops from Saxony?"