Valdemar I
After the civil war, Absalon led warring against the Wends, just like his grandfather Skjalm Hvide had done. At Absalon's instigation, Valdemar I declared war upon the Wends, who were raiding the Danish coasts. In 1158, Valdemar I erected the Sønderborg Castle (Valdemar IV of Denmark and Helvig of Schleswig were married there two centuries later) for protection against the Wends and as part of a larger system of fortifications.