wilboman : I envision the original Bannor as somewhat akin to Numenoreans, aging significantly slower than their later (and watered-down) kin.
In this case the Bannor would be a very racistic society as well, as they would see themselves as superiour, having survived hell and all.
Therefore Bannors 'liberating' a foreign can be imagined in three different ways.
1) The Benigh Colonalism: In this approach the Bannor would see others as inferiour and weak because of mental, physical and educationary underdevelopment. But their conclusion would be that they have to take extra responsibilities for the weak and therefore unite the world under their rule to protect the people from the evil and the hell.
If Bannor would conquer an evil cities they would exterminate all leading people, but they would deliberately spare the common people. Their goal would be to teach the 'Natives' the Bannor way in order to bring them "into the light"
(this would be most similiar with the attitude of the Soviets towards their neighbours (especially their Asian neighours) and of the Colonial Powers in the 19th Century towards the natives in their Colonies)
2) The Islam Way: In this case the Bannor would see themselves as following a superiour way of life and religion (Order). They would conclude that it is their responsibility to spread the (their) truth among the world, but they would use sword and speech to convert newly conquered citizen their course. However the Bannor would also tolerate pockets of other cultures within their borders (as long as the same swear an oath to Bannor and pay taxes).
(The early caliphate of Bagdad is certainly the best example for this kind of state)
3) The Nazi Way: In this interpretation the Bannor would understand themselves as a Master Race thanks to their longetivity and history.
They would therefore forcefully brainwash 'good' and 'neutral' citizen of conquered territory, but merciless extinguish all 'evil' people. They would not distinguish between the nature of a state and its inhabitants. For the Bannor the citizen of evil states are corrupted entirely and can only be cleansed by fire. This is certainly the most extreme interpretation of Bannor Society.
(Nazi Germany or Spain during the time of the Inquisition is the best way to envision this kind of society)
Most probably there might be all three movements present in the Bannor society and all them trying to receive an upper hand in the state and to influence the rulers to follow their philosophy. So Bannor policy might differ from time to time dependent on which movement has the ears of the rulers at a given time.