The king himself was affected as he uttered these words, and tears moistened the eyes of many of the stern warriors who surrounded him.  With general acclaim they approved of his plan, voted him all the succors he required, and enthusiastically offered their own fortunes and lives to his service.  Gustavus assembled a fleet at Elfsnaben, crossed the Baltic sea, and in June, 1630, landed thirty thousand troops in Pomerania, which Wallenstein had overrun.  The imperial army, unprepared for such an assault, fled before the Swedish king.  Marching rapidly, Gustavus took Stettin, the capital of the duchy, situated at the mouth of the Oder, and commanding that stream.  Driving the imperial troops everywhere before him from Pomerania, and pursuing them into the adjoining Mark of Brandenburg, he took possession of a large part of that territory.  He issued a proclamation to the inhabitants of Germany, recapitulating the arbitrary and despotic acts of the emperor, and calling upon all Protestants to aid in an enterprise, in the success of which the very existence of Protestantism in Germany seemed to be involved.  But so utterly had the emperor crushed the spirits of the Protestants by his fiend-like severity, that but few ventured to respond to his appeal.  The rulers, however, of many of the Protestant States met at Leipsic, and without venturing to espouse the cause of Gustavus, and without even alluding to his invasion, they addressed a letter to the emperor demanding a redress of grievances, and informing him that they had decided to establish a permanent council for the direction of their own affairs, and to raise an army of forty thousand men for their own protection.

Most of these events had occurred while the emperor, with Wallenstein, was at Ratisbon, intriguing to secure the succession of the imperial crown for his son.  They both looked upon the march of the King of Sweden into the heart of Germany as the fool-hardy act of a mad adventurer.  The courtiers ridiculed his transient conquests, saying, “Gustavus Adolphus is a king of snow.  Like a snowball he will melt in a southern clime.”  Wallenstein was particularly contemptuous.  “I will whip him back to his country,” said he, “like a truant school-boy, with rods.”  Ferdinand was for a time deceived by these representations, and was by no means aware of the real peril which threatened him.  The diet which the emperor had assembled made a proclamation of war against Gustavus, but adopted no measures of energy adequate to the occasion.  The emperor sent a silly message to Gustavus that if he did not retire immediately from Germany he would attack him with his whole force.  To this folly Gustavus returned a contemptuous reply.