Valdemar I
In 1175, Valdemar I also erected the Vordingborg Castle as a defensive fortress, and as a base from which to launch raids against the German coast. After the death of Absalon in 1201, Valdemar II (reign: 1202–1241) – the second son of Absalon's stepbrother Valdemar I – led a Danish expedition across the Elbe river to invade Holstein, the region between the rivers Elbe and Eider. Holstein is the southern half of Schleswig-Holstein, which is the northernmost modern-day state of Germany.