Karl Gustav, the Swedish king, was campaigning in Poland, but as soon as he could turn around he marched his army against Denmark, scattered the forces that opposed him, and before news of his advance had reached Copenhagen knocked at the gate of Denmark demanding “speech of brother Frederik in good Swedish.”  A winter of great severity had bridged the Baltic and the sounds of the island kingdom.  In two weeks he led his army, horse, foot, and guns, over the frozen seas where hardly a wagon had dared cross before.  Great rifts yawned in their way, and whole companies were swallowed up; his own sleigh sank in the deep, but nothing stopped him.  Danish emissaries came pleading for peace.  He met them on the way to the capital, surrounded by his Finnish horsemen, and gave scant ear to their speeches while he drove on.  Before the city he halted and dictated a peace so humiliating that one of the Danish commissioners exclaimed when he came to sign, “I wish I could not write.”  Perhaps the same wish troubled the conqueror’s ambitious dreams.  The peace was broken as swiftly as made.  In five months he was back before Frederik’s capital with his whole army, while a Swedish fleet anchored in the roadstead outside.  “What difference does it make to you,” was the contemptuous taunt flung at the anxious envoys who sought his camp, “whether the name of your king is Karl or Frederik so long as you are safe?” He had come to make an end of Denmark.

Copenhagen was almost without defences.  The old earth walls mounted only six guns, with breastworks scarce knee-high.  In places King Karl could have driven his sleigh into the heart of the city at the head of his army.  But for the second time he hesitated when a swift blow would have won all—­and lost.  Overnight the Danish nation awoke to a fight for its life.  King and people, till then strangers, in that hour became one.  Frederik the Third met the craven counsel that he fly to Norway with the proud answer, “I will die in my nest, if need be, and my wife with me.”  With a shout the burghers swore to fight to the last man.  The walls of the city rose as if by magic.  Nobles and mechanics, clergy and laborers, students, professors and sailors worked side by side; high-born women wheeled barrows.  Every tree was cut down and made into palisades.  The crops ripening in the fields were gathered in haste and the cattle driven in.  The city had been provisioned for barely a week and garrisoned by four hundred raw recruits.  Sailors from the useless ships took out their guns and mounted them in the redoubts.  Peasants flocked in and were armed with battle-axes, clubs, and boat-hooks when the supply of muskets gave out.  When Karl Gustav drew his lines tight he faced six thousand determined men behind strong walls.  The city stood in a ring of blazing fires.  Its defenders were burning down the houses and woods beyond the moats to clear the way for their gunners.  The King watched the sight from his horse in silence.  He knew what it meant; he had fought in the Thirty Years’ War:  “Now, I vow, we shall have fighting,” was all he said.