Greater Netherlands (Dutch: Groot-Nederland) or Dietsland ("Dutchland") is a hypothetical monolingual polity formed by fusing the two Dutch-speaking regions of Flanders and the Netherlands. The concept was originally developed by Pieter Geyl, who argued that the two only separated during the Eighty Years' War against Spain in the 16th century. Although Geyl was strongly anti-Nazism and argued from a historical and cultural perspective, Nazi Germany built upon the idea during the Second World War with a focus on ethnic nationalism, still prominent among some in the political far right.