Valdemar was the son of Valdemar I., and brother of King Knud, for whom as a prince he fought bravely, putting down the Sleswick rebels, who had been stirred to rebellion by the German emperor, and conquering his enemy, Count Adolf of Holstein. Succeeding his brother Knud in 1202, his first exploit was the conquest of Pomerania, which Knud had won before him. This was now added to the Danish dominions, and in 1217 the German emperor of that date granted to him and the future kings of Denmark all the territories north of the Elbe and the Elde. Thus Valdemar was made master of a great part of northern Germany and ruled over a wider dominion to the south than any Danish king before or after. His success in the south led him to attempt the conquest of the north, and armies were sent to Norway and Sweden with the hope of winning these kingdoms for the Danish crown. In this effort he failed, but in 1219 his zeal for the Church and love of adventure led him to undertake a great expedition, a crusade against the heathens of Esthonia. Gathering an army of sixty thousand men and a fleet of fourteen hundred ships, a mighty force even for the small craft of that day, he quickly made himself master of that stronghold of paganism, great numbers of the people consenting to be baptized. But here he found a new and unexpected enemy and had to fight fiercely for the privilege of carrying the cross of Christ to the heathen Esthonians. His new enemies were the Knights of the Sword, of Livonia, who declared that the duty of converting the pagans in that region belonged to them, and that no other Christians had the right to interfere. And from this ensued a war in which fierce battles were fought and much blood was shed, for the purpose of deciding who should have the privilege of converting the heathen. It is doubtful if ever before or since a war has been fought for such a purpose, and the heathens themselves must have looked on with grim satisfaction to see their enemies cutting each other's throats to settle the question as to who had the best right to baptize them. In one of the battles with the heathens, while Bishop Andreas, the successor to Bishop Absolon, was praying on a high hill with uplifted hands for victory, there suddenly fell down from heaven the Danneborg, the national standard of Denmark. At least, that is what legend tells us of its appearance. It is held to be much more probable that this banner, bearing a white cross on a blood-red field, was sent by the Pope to Valdemar as a token of his favor and support, and that its sudden appearance, when the Danes were beginning to waver before the pagan assaults, gave them the spirit that led to victory. The result, in those days of superstition, naturally gave rise to the legend.