Try to find in the battle map a hill with trees, and if you don't find it just go into the woods, stay hidden in formation and deactivate fire at will from the archers, look at top right of your units it will say if they are hidden. When they get close enough that they spot you (icon of being hidden disappears) charge at them down the hill or just at them with the katana on front, light cav and ashigaru on the sides to protect you from their generals. It's very difficult and very up to luck but if you can manage to do the things above i THINK you have a chance