[quote=thewizardguy]
Well, one cannot negate terrain advantages. If the northern lands are covered in forests, it's quite possible that the natives simply used their knowledge of the environment to prevent any attacking campaigns. The environment and terrain can absolutely decimate an army. A recent example would be Hitler's march on Russia, where his army was incapacitated by the Russian Winter, despite the russians having far inferior weapons and technology.
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Correct, and again going back to Ancient Rome - the Romans could not defeat the Germans, largely because the dense forests played havoc on their organised formations and battle tactics that were suited to open ground.