The united forces of the Emperor and the Catholic League were broken. Gustavus now reaped the benefit of all his smaller conquests. Of the great Imperial army but two thousand remained, with Tilly old, discouraged and discredited. The peasantry fell upon Tilly's retreating army and almost annihilated it. On every side rang the words of a rude song of the period, "Fly, Tilly, fly!" It was howled and hissed and yelled by the peasantry till he had fled far southward. Tilly was heartbroken as much by the hate shown his men in retreat as by the disasters of the battlefield.
Gustavus now had full liberty to go wherever he desired. Richelieu expected the King of Sweden to march at once to Vienna. The Elector of Saxony urged the same course. When Oxenstiern came, soon after this, on a short visit and met his king at Mainz he said plainly: "I would rather have proffered my congratulations at Vienna." But the king thought differently; he knew the wily electors who might at any time stab him in the back, and he doubtless understood Ferdinand's hereditary position, that, though driven from Vienna he would have the heart loyalty of all Catholics and many Protestants as Emperor of the Holy Roman Empire, and Gustavus believed such a course would greatly protract the war.
Gustavus said, "First pure, then peaceable;" so as he passed through the country having churches rebuilt, property restored, and above all, restoring hope and courage to the desolated provinces, he was everywhere hailed as a friend and deliverer, and just for a short time in the lull after the battle, it looked as if his work were really done.
Even after this great battle he continued to preserve perfect discipline; every morning public prayer was offered to God, and Gustavus, with bared head stood before his victorious army leading them in a hymn of thanksgiving. What an object-lesson in godliness it was alike to the pious and the impious, not alone for that age, but for all time to come.
The defeat of the Imperialists at Breitenfield settled the fate of the Edict of Restitution. At Vienna pious Catholics wondered "if God had indeed turned Lutheran."
At Halle, Gustavus divided his army. He sent the Elector of Saxony into Bohemia, which was most anxious to shake off the Imperial yoke. The King of Sweden may have remembered that Bohemia was Ferdinand's crown lands and the Elector of Saxony would by that act forever exclude himself from Ferdinand's favor and be most fully committed to the perpetual alliance with Sweden. Gustavus himself undertook to march over all western Germany and to crush out the Catholic League in its different centers.
Even the Catholics who had been so badly treated by Tilly's army, seeing the good conduct of the Swedish troops, came out to meet Gustavus and greeted him as the liberator of the country. His march through Thuringia and Franconia to the Main and the Rhine reads like a triumphal procession.
The Duke of Saxe-Weimar now joined forces with Gustavus. He proved to be a skillful general and was useful in many ways, especially because of his familiarity with the country.
As Gustavus approached Wurzburg the Catholic bishop of that city, so noted for his persecution of Protestants, fled and left his people to the mercy of the invaders. The city surrendered without any resistance. The king considered that as the country had been abandoned by its rulers the sovereignty became his, so he appointed a cabinet, one-half of whose members were Protestants. He restored to the Protestants their churches and encouraged the Catholics to attend their own churches, and to put them in repair. Only those who refused to submit were severely dealt with. He was really the first prince who understood religious toleration. In every place he claimed that as God's dealing is personal to each individual, each person should have liberty of conscience.
On one occasion when a Catholic town had been captured, his officers suggested that here he could revenge Magdeburg. The king answered, "I have come to break the chains of slavery and not to forge new ones. Let them live as they have done hitherto."