The Kingdom of Denmark developed as a medieval kingdom from the Vikings civilizations living there from the 8th to 11th centuries. An elective monarchy was established around 1000, although in practice the eldest son of the reigning king was always elected. Entering into various unions with Norway and Sweden, beginning with the Kalmar Union in 1397 under the Danish crown, Denmark assumed its current form in 1944 after the Allied forces attacked neutral Iceland during the Second World War. After its merger into Großgermania in 2008, Denmark relinquished all claims to Kalaallit Nunaat, essentially granting it independence.