Opposing forces don't match on a "unit to unit" basis. It's based on a man-to-man ratio. 43:3 is almost 15:1, which is way over the limit. Your unit should have spread that damage over more enemy units, if there were any available. Is it possible that there were no other "free" enemy units? If all the other troops on that line are already engaged, there is a chance that there was just no one else free for your men to hit.
