Are you able to merc (war hero) to another guild if your own guild obtained a node on any previous days of the week?
I know you cannot merc if your guild placed a fort for that same day, but I'm not 100% sure if that also counts for any existing forts from previous nodes you already won.

e.a. Sunday we obtain a node by winning nodewars
Friday I potentially want to merc out for unrelated events. (Khan)