The Mani had a mechanism for pausing a blood feud: the treva, a sworn truce. Harvest needed hands, a festival needed peace, a common enemy needed everyone's rifles pointed the same direction — so the families swore, and the feud held its breath. Breaking that oath wasn't tactics. It was the deepest transgression the culture knew, worse than the killing that started the feud, because the killing only spent blood. The broken oath spent the thing that made truces possible at all.
Somewhere in The Grave He Digs, an oath breaks. Building toward that was the hardest craft problem in the book, and what I learned is mostly about restraint.
An oath scene is easy to write badly because the words of a vow are cheap — any character can say I swear. The work is everything you load onto the oath before it's tested: who witnesses it, what each party gives up to make it, what daily life quietly starts depending on it. A reader has to feel the truce the way the villagers do — as infrastructure. You establish it the way you'd establish a bridge everyone crosses; you let chapters of ordinary weight travel over it. Then, when it goes, you don't write the collapse. You write the silence where the bridge was, and everyone standing on the banks doing the arithmetic.
The other discipline: the unsayable stays unsaid. The characters who break oaths in fiction that lasts are never the ones who explain themselves. The moment a betrayal is fully articulated, it shrinks to the size of its explanation. Leave it partly dark and it stays the size of the culture it broke.