Here is a US Army Air Force picture of April 1945 showing a disassembled 28 cm Mrs 602(f) (formerly French “mortier de 280 mm sur chenille St-Chamond”, actually a howitzer) in a bombed Opel’s plant in Russelsheim, Germany. The tracked carriage can be seen behind the barrel and the Canadian war correspondant Margaret Ecker. Note that the marking mentioned in the caption should read “1918 – Le Havr
e” and not “1918 – Le Harr
Do we know if the Germans actually used these SPGs in operation e.g. Leningrad or Sebastopol?