The victory of Breitenfeld placed all north Germany at the feet of the Swedish king. Perceiving at a glance that even a successful attack upon Vienna would not end the war, and recognising that his first duty was to the troubled Protestants of the centre and of the south, Gustavus marched straight into the heart of Germany on the Main and the Rhine, disregarding the characteristic suggestions of Wallenstein that they should divide Germany between them at the expense of the Emperor and the Catholic party. On October 10th he occupied Würtzburg. The 18th of November saw him at Frankfort on the Main, the old capital of Germany. He spent Christmas Day at Mainz, and there in the fair and rich Rhineland he rested his tired troops, while in the north Tott was completing the reduction of the Mecklenberg coast line, and the Protestant administrators who had been ousted under the Edict of Restitution were being replaced. No one, however, knew better than Gustavus on what slender foundations his power rested. Richelieu was already beginning to think that his ally was becoming too powerful. Louis XIII., it was said, had been heard to mutter ‘It is time to put a limit to the progress of this Goth.’ Force, far more than inclination or policy, had brought him the Saxon alliance, and force might easily break the bond which it had forged. Tilly was mustering new forces beyond the Danube, and at any moment a general of reputation might stamp his feet and produce an army of soldiers of fortune on his flank or in his rear. Even the Protestants could not be trusted should misfortune come. Except at Nuremberg and a few other places, which had felt the hand of the oppressor, there was no enthusiasm in Germany for the Protestant Liberator. Two things were necessary to secure the fruits of the victory which he had won. [Sidenote: =His schemes for a general Protestant alliance under Sweden.=] He must crush the enemy before he had time to recover from the blow of Breitenfeld, and he must gain a basis of military operations and political influence by uniting the Protestant states in a firm league under his leadership. With Tilly destroyed, and the _Corpus Evangelicorum_ formed, and trusty Swedish captains placed in occupation of the ecclesiastical lands of central Germany, then and not till then might Gustavus consider his work secure. [Sidenote: =Advance upon the Danube to Munich, 1632.=]