Since the 1899 21cm mortar was missing a recoil recuperation system, Krupp began in 1902 the study of a modernisation. The new 210 mm was delivered from 1910, this time equipped with a recuperator, as well as other improvements.

216 such mortars equipped the German Armies at the conflict outbreak, and were named '21 cm Morser M10', or 'der Mörser'. That mortar needed 3 'cars' for its transportation in separate loads : the carriage, the tube transportation car, and the accessories car.

In 1916, a new modernisation (including the systematic addition of a protection shield) and the extension of the tube length from 12 to 14.6 calibres transformed it into the 'lange 21 cm Morser M16', one of the famous aces of the heavy German artillery, providing an impressive destructive power on all the fronts, with its big 120 kg shells being sent to an impressive 10 km distance...

Moreover, the tube could now be transported directly lying on the carriage, reducing the number of cars needed to transport the gun to two.

'lange Mörser' was slightly modified a last time in 1917, mainly to re-inforce its wheels to allow the mechanical towing by a single tractor, and was called back to service during WW2.

Main characteristics :

• Weight in firing position : 7380 (M10) - 7550 kg (M16 Langer)
• Calibre : 211 mm
• Tube length : 12 calibres (M10) - 14.6 calibres (M16 Langer)
• Projectile weight: 120 kg
• Initial velocity :367 m/s (M10) - 394 m/s (M16 Langer)
• Maximum range : 9400 m (M10) - 10200 m (M16 Langer)
• Elevation range : +6 / +70 degrees
• Direction range : 4 degrees