History has no record since the days of Attila of so frightful a massacre. Neither age nor sex was spared, and 30,000 men, women, and children were ruthlessly massacred. The result for a time justified the anticipations of the ferocious leader. The terrible deed sent a shudder of horror and terror through Protestant Germany. It seemed, too, as if the catastrophe might have been averted had the Swedes shown diligence and marched to the relief of the city; for in such a time men were not inclined to discuss how much of the blame rested upon the shoulders of the Duke of Brandenburg, who was, in fact, alone responsible for the delay of the Swedes.

Many of the princes and free towns which had hitherto been staunch to the cause of Protestantism at once hastened to make their peace with the emperor. For a time the sack of Magdeburg greatly strengthened the Imperialist cause. No sooner did the news reach the ears of the Duke of Brandenburg than his fears overcame him, and he wrote to Gustavus withdrawing from the treaty he had made, and saying that as Spandau had only been delivered to him in order that he might march to the relief of Magdeburg he was now bound in honour to restore it.