It refers to the land campaign starting with the 6th June landings in Normandy and ended with Field Marshal Montgomery taking the German military surrender of all German forces in the Netherlands, Northwest Germany and Denmark on Lüneburg Heath in Northwest Germany. The campaign was conducted by Supreme Headquarters, Allied Expeditionary Force, of which the British 21st Army Group was a component, along with the American 12th and 6th Army Groups. Together, the three army groups comprised the Allied effort on the Western Front which at its longest stretched from the North Sea to Switzerland.