[] Try to flee. You still have a day before his warriors are in Riverbend.
-[] Flee immediately to keep as large a distance to the pursuers as you can.
-[] Attempt to keep good order and make certain that their are at least some scouts ahead to make sure nothing lies in our path.
Eesh, this is a mess reading through it. Ultimately I would like to point out a few things anyway 1: We have so far only targeted Brushcrest in raids, their fellow coalition members have no reason to help them strike the north-eastern mountain raiders who have so far only hit Brushcrest, instead of the the very large and currently very dangerous religious manics that they are all being regularly hit by. 2: We have stone walls. The only way we are losing the main Greenvalley settlement right now is by starvation and it hasn't been quite long enough for our food stocks to have run out quite yet. 3: We have our religious proto-vassals in the form of the White Clans up north, who will be extremely pissed if Brushcrest does hit the Temple and by extension us, meaning, they will be hitting any besieging force that is at Greenvalley.
To put it short, Greenvalley is very likely safe.
All the same, this guy and the Author's note has just shown us Brushcrest is not to be trusted and has in addition broken a blood sworn oath by tattling our plans to the Makar in order to get us killed, a perfectly valid cause for pulling out of the war. The Brushcrest coalition, even if they are fighting the Makarites, must do it without us due to this betrayal. Let us return home for now, and plan retaliation with help from the white clans, who will be more than happy to help us strike sacred oathbreakers who betrayed their religious leaders. Perhaps we could even encourage the clans to come wholesale down from the mountains and replace the river tribes with some far more appreciable neighbors.
Edit - Plan still stands, but as for the more immediate situation I'm willing to trust Satar's idea and our warrior's ability to maintain their oaths. Army reforms were likely to get out within 3 turns anyway, this just means Makar get them in two instead of three, besides, our warriors might even be able to add underlying elements of the faith of bones to the Makar, religions are certainly young and compatible enough that we might be able to get them to consider that Makar is just a truly great Ancestor beyond any other and even now whispers into the ears of the chosen, instead of a wholesale god. The collection of the ancestors will certainly be popular enough among less skilled warriors and civilians, who would now have a chance to meet him regardless of how much (or little) attention they may receive in life.
[X] Do something else
-[X] When the Chosen returns, make him a counter offer. Since you were both played against the other by the sowing men, you will show them the consequences of trying to trick their betters
-[X] Together follow the river down to strike at the Great Hearth, punish the plainsmen and claim tribute for Makar and their ancestors alike
-[X] If the Chosen doesn't accept then:
-[X] Accept the deal.
--[X] Give up one unit of warriors, picked by the Chosen.
---[X] All Greenvalley warriors will swear blood-oaths to never teach anyone their skills.