My story has a battle between two tiny races of humanoids. Assume that both of these races have developed in relative isolation from one another so they have not had a lot of time to develop specialized weapons and tactics against each other's strengths and weakness or steal each other's technology.
Gnomes average 20-30cm (8-12in) tall. They basically look like your average variety garden gnomes. They are rather strong for their size, but are limited by their proportionally shorter appendages. Their level of technology is roughly comparable to 12th century Europe.
Their opponents are the Gremlins which average 30-40cm (12-16in) tall. They weigh about the same as the gnomes, but are faster and have longer appendages. Their level of technology is much more comparable to the Late Bronze Age. They are no less clever than gnomes or humans, their civilization is just not as far along.
My original concept was to basically make it a stereotypical dwarves vs orcs kind of conflict, but then it occurred to me that these guys are much smaller than orcs or dwarves. Thanks to the square-cube law, this makes them proportionally stronger and tougher than you would expect out of humanoids. The gremlins would reasonably be able to jump like cats and climb like squirrels and the gnomes would be able to wield weapons and armor that are much thicker and heavier for their body size than you would expect. It also means both sides have much shorter acceleration arcs when swinging/throwing/shooting weapons. So with all of these factors in play, it seems to me that the very nature of weapons, armor, and tactics would have to have to change to make since for these tiny humanoids.
What kinds of armaments and tactics would each side most likely use the first time they meet in battle?
In case it matters, the battlefield is the inside of a 16th century human barn and neither side wants the barn to be destroyed.
Also, neither side has access to magic or explosives of any kind.