It's not Istvan's Theme but you're right you heard this tune elsewhere - i.e. here:
open.spotify.com/track/18JsUβ¦
That's KCD1. After Skalitz is attacked, Henry discovers pile of bodies in St.James village which was burned to ground. (TC 0:55).
In KCD2: when Henry loses the duel with Dry Devil at Maleshov, another village will be burned and another innocent people killed. And this time, Henry's on the side of perpetrators.
Hence why I used this motif here again: "War is a nasty business" moment.
Doea that make sense?