If these were the views of Gustavus--and though he never formally announced them to the world his whole subsequent conduct gives reason to believe that he had already entertained them--it becomes not so very hard to understand why he decided upon marching upon the Rhine, and despatching the Elector of Saxony to rouse Bohemia. It is true that Oxenstjerna, the prudent Chancellor of Sweden, wise after the event, used to declare that his master had made a mistake, and later military historians, fancying that Vienna was in the days of Gustavus what it was in the days of Napoleon, have held that a march upon Ferdinand's capital would have been as decisive as a march upon the same capital in 1805 or 1809. But the opinion of Gustavus is at least as good as that of Oxenstjerna, and it is certain that in 1631 Vienna was not, in the modern sense of the word, a capital city. If we are to seek for a parallel at all, it was rather like Madrid in the Peninsular War. The King had resided at Madrid. The Emperor had resided at Vienna. But neither Madrid in 1808 nor Vienna in 1631 formed the centre of force. No administrative threads controlling the military system stretched out from either. In the nineteenth century Napoleon or Wellington might be in possession of Madrid and have no real hold of Spain. In the seventeenth century, Ferdinand and Gustavus might be in possession of Vienna and have no real hold on Austria or Bohemia. Where an army was, there was power; and there would be an army wherever Wallenstein, or some imitator of Wallenstein, might choose to beat his drums. If Gustavus had penetrated to Vienna, there was nothing to prevent a fresh army springing up in his rear. [Sidenote: § 9. Necessity of finding a basis for his operations.] The real danger to be coped with was the military system which Wallenstein had carried to perfection. And, in turning to the Rhine, Gustavus showed his resolution not to imitate Wallenstein's example. His army was to be anchored firmly to the enthusiasm of the Protestant populations. There lay the Palatinate, to be freed from the oppressor. There lay the commercial cities Augsburg, Nüremberg, Ulm, and Strassburg, ready to welcome enthusiastically the liberator who had set his foot upon the Edict of Restitution; and if in Bohemia too there were Protestants to set free, they were not Protestants on whom much dependence could be placed. If past experience was to be trusted, the chances of organizing resistance would be greater amongst Germans on the Rhine than amongst Slavonians on the Moldau. [Sidenote: § 10. He resolves to march to the south-west.]