A Tachanka was a carriage with a rear firing maximum gun used primarily in the Ukraine and related areas. It was a support weapon for cavalry formations in the first and second World Wars, the Russian Civil War and the Russo-Polish War.
I put one of these together and painted it. I have to say the model is great. The crew are in in WWII uniforms but heads could be swapped to make earlier examples.
The Tachanka is always associated with Nestor Makhno, the anarchist leader in the RCW, who used them extensively.
There are all sorts of theories about how the word Tachanka was derived from various Ukranian or Russian language sources but the truth is no one knows. It is, however, as iconic to cavalry warfare on the Ukrainian plains as the Spitfire is to the Battle of Britain.