This topic seems to be a bit dead at the moment, so I will try adding another point for discussion.
Who would win?
20,000 men of the Imperial Roman Army (including 8,000 Legionaries, 10,000 Auxiliaries and 2,000 Praetorians)during the reign of Marcus Aurelius and lead by none other than Marcus himself VS. 20,000 men of the Han Dynasty Government Army lead by Cao Cao (A warlord, chancellor of Han and later the state ruler of the kingdom of Wei). This battle takes place in mountainous terrain, with steep and narrow passes through mountains with no flat land and a dense forest off to one side. Each side has all of their respective technological war machines & strategies to play with. The weather is dense fog in the morning, with a clear day by noon, and heavy rain by evening (plus a thunderstorm at night).
I think this is a tough one, both sides were highly organised and disciplined and were known to be masterful at the art of warfare.