Historical firearms article on the gun.

Highlights:

The first untethered balloon flight took place on the 21st November 1783, with the first military use occurring during the French Revolutionary Wars. During the Franco-Prussian War the French again used observation balloons and when Prussian troops besieged Paris they became a vital lifeline out of the encircled city.

[In response to balloons] Alfred Krupp developed a breech-loading 37mm canon mounted on a pedestal fixed to the bed of a carriage. Some sources describe the gun as a Ballonabwehrkanone or balloon defence gun. The canon had a stock and a folding sight fixed to the receiver. The canon could be rapidly deployed to open fire on the balloons as they crossed Prussian lines. Five French balloons were captured by the Prussians when they were forced to land, a further three were declared missing.