The First World War will forever remain in the memory of mankind. It will remain not only because of the monstrous number of victims for those times, but also due to the rethinking of the art of war and the emergence of many new types of weapons. So, for example, the widespread use of machine guns as cover for dangerous areas drew the development of mortars and light field artillery. Aircraft (naturally, enemy) became the reason for the appearance of anti-aircraft artillery and so on.
In addition, the artillery and mortars also had their own problems - soon after the start of the shelling, the enemy, using various methods, determined the approximate area from where they would be fired at, and opened fire back. Of course, in such artillery duels there was nothing good for both sides: both there, and there, the soldiers had to do their job, risking to catch the shrapnel or die. In this regard, it was easiest for the mortar men: their small weapons were much more mobile than the "full-fledged" guns. Having made several shots, the mortar crew could leave the position before the enemy covered it with return fire. Due to the weak development of aviation during the First World War, the main way to determine the position of enemy artillery was "by ear" detection, which was carried out by sound reconnaissance units. The essence of their work was as follows: if it is known where the "listeners" posts are located, and there is information about the direction of the sound source (shots) relative to the posts, then calculating the approximate location of the enemy weapon is not a particularly difficult task.
Accordingly, the simplest means of countering sound reconnaissance would be the absence of sound when fired. At first glance, nothing complicated, but do not forget about the practical implementation. This task seemed quite difficult to the military of different countries, and not everyone took up its implementation. As a result, serial silent mortars will appear only in two countries - Austria-Hungary and France. However, they will never succeed in ousting their "classical" brothers.
The first were the Austrians. Probably, the experience of limited operation in the troops of the Windbüchse air gun designed by Girardoni affected. In 1915, the first batch of 80-mm pneumatic mortars went into the trenches. In appearance, the weapon turned out to be simple: a frame of two triangles on which the swinging barrel is located, and under it is a base plate with a compressed air cylinder. On the left side of the frame, a sector was installed with the marking of the elevation angles. Also on the left, but already on the axis on which the barrel was attached, a lever for setting the elevation was placed, which at the same time served as an angle indicator arrow. The shot was fired by short-term opening of the valve on the cylinder, the dispenser was not provided. So that the inept soldier did not "release" all 270 atmospheres in one shot, they used a new form of mine and the method of launching it. In its shape, a mine for a pneumatic mortar was more like an ordinary artillery shell - the plumage was removed from it. On the side surface, in turn, added several round protrusions of soft metal. The shot of a new mine took place as follows: when loading the mortar (from the breech), a special disposable obturator was put on the rear of the mine, and the mine was inserted into the chamber. Then the breech was closed, aiming was carried out, and the valve on the compressed air cylinder was opened. Until a certain moment, the mine was held in the chamber due to the contact of its protrusions with the protrusions on the inner surface of the barrel. When the pressure rose to the required 35-40 atmospheres (for an 80-mm mortar), the soft metal of the mine stops crumpled, and the ammunition flew out of the barrel with good acceleration. After the mine was sent "to visit" the enemy, the soldier had to close the cylinder valve. Simple and tasteful.
Yes, only the pneumatic mortar did not become an absolute weapon. Its maximum firing range was within 200-300 meters, depending on conditions. At first, they tried to change the range also by the amount of air supplied, but with the used mine holding system, such an adjustment could not be brought to practical use. However, the available range was quite enough to throw "gifts" into the nearest enemy trenches. But the balloon delivered the most trouble to the soldiers. Firstly, because of its thick walls, the mortar turned out to be very heavy, and secondly, metallurgy did not yet allow making the gas tank relatively strong. So any fragment or even careless handling could lead to bad consequences, from a simple release of pressure to an almost explosion. Another disadvantage of the balloon was the pressure drop. The shots themselves reduce it, in addition, the weather also affects. The sun hit the balloon - the pressure increased, and with it the firing range at the same elevation. It started raining, pretty wet and cooled the cylinder - the pressure dropped along with the range. Finally, the bottle needs to be “recharged” from time to time, and this requires a compressor - a soldier with a hand pump will take an indecent long time to refuel. The compressors, on the other hand, were too large and uncomfortable at the time to be kept in trenches or dugouts right at the front.
Another country, after weighing the pros and cons of pneumatic mortars, would probably refuse them. But the Austrians decided otherwise and already in 1916 launched the production of weapons of large calibers: from 120 to 200 millimeters. In the course of their operation, one characteristic and useful feature of the pneumatic weapon became clear: the projectile accelerated in the barrel smoother and with much less acceleration than in the powder. Thus, from a large-caliber pneumatic mortar, it was possible to shoot ampoules with toxic substances without the risk of their destruction in the barrel. By the end of the war, almost all pneumatic mortars were transferred to such "work".
However, at the end of the war (by the way, for Austria-Hungary it ended very badly) pneumatics left all classes of weapons except small arms, and even there they are used exclusively in sports and hunting. Pneumatic field weapons of other countries were also short-lived in the troops. Since the interwar period, such projects, although they appear from time to time, have become the lot of single projectors and artisans. Serious gunsmiths abandoned this idea.
