There were probably not many fights at night, at least none that I ever heard of. Probably on a smaller scale, raids and the like, but not large battle between armies. There were probably even less fights in the night, in a forest, which is quite often the case in Battle Brothers.
There were quite a few small scale “ambush” type of engagements, if not major formation battles.
Anyways, I simply avoid fighting at night and in forests, if I can help it. The current AI ranged behavior and the sight radius deficiency all make such situations more painful than having my colon removed (well, this hasn’t happened, but you get the idea, since a friend who’s had it done says it’s horrible).