Historic context :
The 58 n°1 trench mortar designed by the Commandant Duchêne was widely appreciated on the French frontline as soon as January 15 in the trench warfare. But although the exceptional celerity of its development allowed to answer to the emergency situation faced by the French armies missing this kind of weapon, it did not leave time for bringing solutions to its relative instability and the relative lack of power of its 16 kg bomb, nor improvements to some balistic properties such as precision and range.
Therefore, immediately after the frontline firtst shots of the new weapon, the Commandant Duchene was asked to go back to Bourges and design the next generation of this too rudimentary : the new version came real quick, more robust, equipped with a more stable carriage, orientable in direction by pivoting against a curved plateI, with improved range, and able to throw bombs more powerful than the 16 kg fin-tail bomb.
The result of this once again rapid development made again by the Commandant Duchêne and of the Ateliers de Bourges, under the supervision of the General Dumézil, was named 'mortier de 58 n°2', and directly ordered to a Saint Etienne private manufacturer as soon as the second week of February 1915 (140 pieces). Deliveries to the armies started from April 1915.
The weight increase was moderate so that the weapon remained transportable to the first lines by men or donkeys in several loads or on a wheeled trailer, with its accessories including a wooden beams base. The improvements allowed the mortar to fire a larger variety of different weight fin-tail bombs (16 kg bomb of the mortier de 58 n°1, 40 kg 'D' bomb, 18 kg 'LS' bomb, 35 kg 'DLS' bomb, 20 kg '1917 A' bomb, ...) to distances from 445 to 1450 m.
This exceptionally robust and simple weapon was reckognized a great success. Starting with 498 pieces in october 1915, the French army owned more than 815 such mortars in march 1916, 1268 in may 1917 and 2396 in January 1918. There still 1699 by November 1918. Several improvement were bring during the war, including different wooden bases, the integration of a wheeled screw for the vertical pointing, and a percussion firing device (Forgeat).
This mortar was the backbone of the French trench artillery and was used efficiently on all fronts. Its quantities were 276 in June 1915, 779 in March 1916, 1268 in May 1917, 1766 in January 1918 and 1158 in November 1918. It was in service in several France allies armies such as Belgium, Italy and USA.
Technical data :
- Complete description : 58 Nr 2 trench mortar
- Design year : 1915
- Calibre : 58.00 mm (tail of the projectile)
- Weight in firing position : 410 kg
- Weight for transportation : 600 kg on wheeled trailer
- Tube length in calibres : 8.00 (550 mm)
- Grooves : 0 (smooth bore)
- Projectile weight : plusieurs bombes : 16 kg ('A' et 'B') / 40 kg ('D') / 18 kg ('LS') / 35 kg ('DLS') / 45 kg ('45 kg') / 20 kg ('ALS') / 19 kg ('WD')
- Initial speed : 80 m/s ('A' and 'B') / 67 m/s ('D') / 117 m/s ('LS') / 83 m/s ('DLS') / 63 m/s ('45 kg') / 129 m/s ('ALS') / 129 m/s ('WD')
- Fire rate : 1 shot / 2 min, then 1 shot / min with the percussion firing system
- Range : 650 m ('A' and 'B') / 450 m ('D') / 1250 m ('LS') / 670 m ('DLS') / 400 m ('45 kg') / 1450 m ('ALS') / 1450 m ('WD')
- Elevation range : 45 to 80 degrees
- Direction range : 35 degrees total range