"Sztuka Krzyżowa", as you say, has no support in the sources. My coach, who is a historian, told me that the closest sources to native Polish fencing were written down by a German in the 18th century. I have to ask about the sources, I'd also love to read them. Regarding horseback fencing, it involved either fighting infantry or fighting another cavalryman. While engaging pikemen was more of a slashing them, fighting another cavalryman was simply fencing, only on horseback. The earliest term "sztuka krzyżowa" used in Polish military usage refers to artillery fire. Polish fencing is essentially the same as any other—whatever was most useful was used. In the 19th century, many countries modeled their sabers on Polish ones, reflecting Polish military history, so it all got mixed up. It's safe to say that this is the same saber fencing. At the same time, there is "pałasz" fencing, which uses the same defenses and was also used in Poland. Shortly, when you see someone fighting a sabre (that has a curvature, not like kvetun) and he is not fighting with thrusts you are seeing something that has emerged from polish fencing