I think it was mostly just Kurita that kept trying to get through the Wall. I doubt most nations list many people to the Wall.
Still, how many were lost before they knew about it and stopped trying?
Republic was losing control of those regions. Thanks to the betrayals of Steel Wolves, Stormhammers, Swordsworn, Spirit Cats, etc. and the conflicts those groups started, the RAF was staring down the barrel of bleeding out within a few years having to fight those and any house getting in on the action. They were losing that territory no matter what happened. Nobody can fight a war of attrition that encompasses effectively 100% of your territory at all times. So Republic executed Fortress Republic, ordering withdrawals from 90% ish of their territory, though it's not clear how much was already functionally lost.
I was curious and tried to figure out how many units deserted. At a glance:
- 4/10 Triarii were wiped out or deserted. VIII ended up with Redburn, and five others (II, IV, VI, VII) made it in the fortress.
- 8/10 Principes were wiped out or deserted. III ended up with Redburn, and X Principes made it in.
- 7/10 Hastati units were wiped out before Fortress republic. None seem to have deserted. VII ended up with Redburn, then II and X Hastati made it in the fortress.
- All of Stone's brigade made it
So 14/36 RAF units may have deserted. But some might have been destroyed outright. I would be surprised if we get more than that barring someone taking a swing in shrapnel
I get being surrounded and needing to pull back. I can also understand having to leave some behind. But in this case, they were not only left behind but the way home slammed shut on them. They either had to fight and die, surrender, or go else where to survive. I would think that would case all oaths of allegiance would be null and void as their realm abandoned them. Since they need to provide for those they can, I don't see a problem with them either joining another house, or becoming mercenaries. I also don't see why others would have a problem hiring them.
Now if a unit showed up intact, with pristine units, from behind the wall, with a transit time that showed they left before their world fell, or was even attacked, then I could see people thinking of them as deserter. Then I would think they either wouldn't hire that unit or would have strict contract in their favor in case that unit takes off.