Another war analogy was the Byzantine defense. Their policy was to avoid decisive, large-scale battles where a lot can go wrong at once. If an enemy army is incurring, first try to weaken or deter it with lighter forces that also gather intel. If they can't stop the threat, form and advance a larger army with a better-planned supply chain to stop it deeper in the territory.

Which actually doesn't work so well in AoE. The game doesn't have a concept of army supplies, so you usually just want a huge unstoppable army you can send anywhere.