One way for things to work out as hinted is for Ansom to attack (perhaps without much support), lose the battle and the pliers. That would give Parson the pliers.

The retreat contigency could come into play on Charlie's turn. Charlie has already said he wanted the mathamacy device (hopefully with Parson) and the pliers. So if Parson gets the pliers, Charlie will attack. Charlie will almost surely be too strong for Parson's forces, especially in the open, so Parson will have to retreat. I think the tunnels are the likely spot.

The tunnels are the easiest to defend. Many of GK's troop get a bonus in the tunnels, I'd guess that a bunch of them leveled (granted they might only be level 2, but are most troops level 1?), and they've got a dirtamancer. It seems likely that the archons will be less effective in tunnels than in an open area.