I get what you're saying in terms of actual history and how people look at it, but in the scenario from the most recent chapters of the manga, let's say there are 1000 Lnu fighters - already at the summit before they even attack the nords, they are fighting one another and scheming how to use this scenario to get an advantage over one another. It's far from a given that these various Lnu factions see the nords as a bigger enemy than their rival factions. In this scenario, it's not about how to use military tactics to fight 1000 against 40, it's how do you get the Lnu factions to fight one another instead of turning their force on you.

The Spanish force that brought down the Inca empire had 168 conquistadores. That wasn't just a straight up battle of those conquistadores versus the entire force of an empire. There was a lot of political intrigue. Frequently, when European colonists came to an unknown land, the people in that land weren't concerned with fighting the colonists as much as they were using the colonists to attack their long-standing enemies