The 120 mm Armata wz. 78/09/31 and 120 mm Armata wz. 78/10/31 were field guns produced in Poland and used by Poland during World War II and Finland during the Continuation War.
History
After the defeat of the Central Powers during World War I the Allies agreed to reconstitute the country of Poland from the territory which had been partitioned by the German Empire, Austro-Hungarian Empire, and Russian Empire. The new armed forces of the Second Polish Republic inherited a mix of German, Russian and Austro-Hungarian weapons from its former occupiers. Poland also received French technical assistance and weapons to rebuild its armed forces after World War I. Large numbers of Russian weapons were also captured during the Polish-Soviet War when the Red Army was defeated after the Battle of Warsaw in 1920.
Background
The 120 mm Armata wz. 78/09/31 and 120 mm Armata wz. 78/10/31 were a combination of the gun barrels from the Canon de 120 mm L mle 1878 field guns supplied by France and the carriages of the Russian 152 mm M1909 and 152 mm M1910 howitzers. The name of the guns signifies the dates of manufacture for each of the components used. 78 indicated the barrel was from 1878, 09 and 10 indicated the carriages came from either the M1909 and M1910, and 31 indicated the design was completed and construction began in 1931.
Design
Cannon de 120 mm L mle 1878
The mle 1878 was a breech loaded gun with a de Bange obturator and used separate loading bagged charges and projectiles. It had a box trail carriage, no gun shield, two wooden-spoked steel-rimmed wheels, an unsprung axle, and no recoil mechanism. The mle 1878 was lighter than its heavier brother the Canon de 155 mm L mle 1877. It had roughly the same range and rate of fire as the Canon 155 mm L mle 1877, but it fired a lighter projectile. The 120 mm L mle 1878 was classified as a siege et de place (stationary siege gun) in France's Séré de Rivières system of fortifications. In line with this mission, the carriage was tall because it was expected that its barrel would overhang a parapet and use its range to provide long-range, low-angle counter-battery fire against enemy artillery. Although an elderly weapon at the time of World War I, it was available in large numbers and its heavy projectile and long-range made it a useful weapon and many were still in use during World War II.
An early drawback of the gun was that it required considerable time to prepare a firing platform made of concrete or timbers before use. An external recoil cylinder was then bolted to the platform and connected to an eyelet on the bottom of the gun carriage. Without it, the gun had no recoil mechanism and when fired the gun rolled back onto a set of ramps behind the wheels and then slid back into position. Since it lacked a recoil mechanism it had to be levered into position and re-aimed after every shot, which was strenuous, time-consuming, and limited its rate of fire. The height of the gun also limited the rate of fire since a gun crew needed to lift an projectile to shoulder height.
Another drawback of the mle 1878 was since its carriage was tall and narrow it was top-heavy and not designed to be mobile. It was found it had a tendency to sink in on soft ground and since it was designed to be pulled at low speed by a horse team its wooden-spoked steel-rimmed wheels and axle were too fragile to be towed at high speed by motor traction. An early modification to make the guns suitable for field use was the fitting of Bonagente grousers to the wheels to improve balance and reduce ground pressure on soft ground. A bonus was they slowed recoil and didn't require extensive site preparation to bring the guns into action. These factors made the mle 1878 unsuitable for anything other than static defense during World War II.
Schneider 152 mm M1909 & 152 mm M1910
The M1909 and M1910 were ordered by the Imperial Russian Army in the wake of the Russian Empire's defeat during the Russo-Japanese War. The Russian Army was in the process of re-equipping with new weapons and at the time the Russian Armed Forces were heavily reliant upon French and German designs. The M1909 and M1910 were designed by the French company Schneider-Creusot and were produced in large numbers under license at the Putilov and Perm factories in Russia. The heavier M1909 was designated a kryepostnaya gaubitsa (fortress howitzer) while the lighter M1910 was designated a polevaya gaubitsa (field howitzer). The two howitzers had similar performance but differed in the arrangement of their recoil mechanisms and gun shields.