I can't help theorycrafting in a game that is so rich in narrative...

But I just started a replay of TW1 so that I could get saves for the Order and Scoia'Tael, and I noticed that Kaer Morehn is "north of Kaedwen." I haven't read the books, but is there any reason why Geratl might choose to support Kaedwen (Roche/Henselt) because the school of the wolf was based there? After all, Letho explains that he chose to carry out the assassination plans of the Empire in the North because the school of the viper was based there.

EDIT: I love that this game's narrative is deep and complex enough to have me wanting to replay its prequel and ask this kind of question.

Letho's working for Nilfgaard isn't so much simply because of location, but -- according to him, who has every reason to lie to you in order to convince you not to fight him -- because the Emperor has offered to help support and rebuild the School of the Viper, which otherwise might be near extinction.

Henselt isn't offering such assistance, and has a genocidal track record when it comes to non-humans. Given that Geralt has memories of dying during a pogrom against non-humans, it is not terribly likely that he would back Henselt even if we ignore the aversion towards getting involved in politics.

Well, the town-and-gown relationship between the Kaedweni locals and the Wolf school was a nasty and bloody one. It would be unlikely that Geralt would hold any loyalty or even affection toward the sons of bitches who laid waste to Kaer Morhen, or their obnoxious king.

And don't forget the Kaedweni citizens attacking at the Kaer Morhen, where Henselt didn't lift a finger to give the citizens the finger.

Oh... above poster already stated it, sorry.