Rus' Khaganate
Walcheren became the seat of the Danish Viking Harald (fl. 841-842), who conquered what would become the Netherlands together with his brother Rorik (fl. 842-873) (or Rurik) in the ninth century. One fringe theory has it that Ahmad ibn Rustah (fl. 10th century) described Walcheren when reporting on the seat of the Rus' Khaganate.