The Austro-Hungarian 37mm Infanteriegeschütz M.15 may have looked like a toy, but in reality it was a pretty potent trench gun.
The gun itself was - like the French counterpart, the 37mm mle1916 - created out of the new and unforseen demands created by the trench warfare. In this type of combat there often araised the need to destroy targets that were very well protected against ordinary indirect artillery fire, regardless if by cannon or howitzer. The most common target of that kind was dug-in, well-protected, shield-equipped Machineguns: the only way to destroy them was to use direct artillery fire. Mountain guns was often used in this role, but even they were often difficult to move and use on the churned-up battlefields. And even if you could bring them into the first line, they were difficult to bring along in an attack.
The solution was seen in a light gun, where very high accuracy would compensate for the relative lightness of the projectiles. Typically the gun would be used to put grenades with pin-point accuracy through the embrasures of bunkers or dug-outs. Such a gun was ordered by the Austro-Hungarian Army in 1915, and already in November that year a prototype was successfully tested on the Southwest front.
Despite problems with the sight, in early 1916 an order for a 1000 guns was placed, and soon the first pieces were delivered to the troops.
The gun, the infanteriegeschütz M.15, could be dismantled into three packs for transports: tube, cradle and tripod, each weighing 34.6kg, 25.3kg and 24.4kg respectively. (It could be transported by manpacks, by horse or by dog-cart.)
The ammo came in boxes of 15, each box weighing 26.5kg. There were three types of grenades: HE, HE/shrapnel and tracer.
In theory each Infantry Regiment should have two infantry gun platoons. Each platoon consisted of 1 officer, 2 NCO:s, 26 men, 1 cart, 4 pack horses and 4 guns. Due to lack of equipment in general each Regiment only got one infantry gun platoon each. They were often employed in the first line, even during defence, but were often kept down in the dugouts until needed.
It was accurate and the theoretical range was up to 3,000 meters. At that range it wasn’t very accurate due to the pretty short gun tube (37.2cm). The longest practical range was 2,200 meters. Also there were complaints regarding the lack of punch in the grenades, at the end of the war the general word was that the calibre was too small, and that a bigger gun was needed for this role.