I'm trying to get an understanding how much the Night King's army could grow on his way south by raising the bodies of people killed during the previous seasons, even without killing anyone else.
I know that the one sure-fire way (no pun intended) to prevent reanimation is to burn the body. Burying them deeply enough might also work but I'm unsure about that. I also have no idea how the state of decomposition might factor into this.
Now there were a couple of notable battles (potentially) providing fodder for the undead army. In which of these did the bodies get burned (or otherwise secured against reanimation) afterwards? And conversely, from which sources can we expect dead fighters to join (or already have joined) the undead army?
- Fist of the First Men - presumably all dead Crows got reanimated
- Wildlings raiding Mole's Town and the Gift - ?
- Wildlings vs. Castle Black - ?
- Craster's Keep (both times) - ?
- Hardhome - everyone was raised
- Stannis vs. Wildlings - I think all the dead were burned, no reanimation possible (?)
- Stannis vs. Ramsay - ?
- Battle of the Bastards - ?
For simplicity's sake, I'm restricting myself to the Northern part of the North, up to about the height of Winterfell. If I forgot any other incidents leading to a relevant amount of casualties, feel free to add them.
I'm primarily interested in the show, but I'm also tagging the books in case they provide some information about the requirements for corpses to be reanimated.