[duncanawoods]

Yes, I think you are right, that counts as precedent.

I was thinking of the famous battles chasing each other around the map that included entrenchment but didn't stall as significantly. I can see an argument that Petersburg is the last stand of an exhausted defeated army digging in at their capital with the attackers choosing to siege rather than purely an unsolvable tactical impasse created by entrenchment technology... but it's probably that too.