The back of the photograph reads, ""A 28-cm German gun abandoned in the November retreat."" This probably refers to: ""The Armistice of 11 November 1918 was the armistice that ended fighting on land, sea and air in World War I between the Allies and their last opponent, Germany. Previous armistices had eliminated Bulgaria, the Ottoman Empire and the Austro-Hungarian Empire. Also known as the Armistice of Compi�gne from the place where it was signed, it came into force at 11 a.m. Paris time on 11 November 1918 (""the eleventh hour of the eleventh day of the eleventh month"") and marked a victory for the Allies and a complete defeat for Germany, although not formally a surrender. The actual terms, largely written by the Allied Supreme Commander, Marshal Ferdinand Foch, included the cessation of hostilities, the withdrawal of German forces to behind the Rhine, Allied occupation of the Rhineland and bridgeheads further east, the preservation of infrastructure, the surrender of aircraft, warships, and military mat�riel, the release of Allied prisoners of war and interned civilians, and eventual reparations. No release of German prisoners and no relaxation of the naval blockade of Germany was agreed. Although the armistice ended the fighting, it needed to be prolonged three times until the Treaty of Versailles took effect on 10 January 1920."" (https://en.wikipedia.org/wiki/Armistice_of_11_November_1918)