The description of the battle tactics is interesting in light of something I really appreciate about the way you have constructed this story. It's something I guess Tolkein did, too, but you are making very intriguing use of it, and that is doubling or redundancy.
Tolkein appears to have built redundancy into the system, so that if one of our protagonists gets killed (or otherwise departs Arda), there is another to take his (or her) place. So Boromir is the back-up for Aragorn, Faramir for Boromir (and by the transitive property, Faramir for Aragorn later), Eowyn for Arwen, Sam for Frodo, etc.
In your story, this seems to be a deliberate device (the presumed doubling of Findulias and Arwen, and an explicitly stated desire of Denethor for redundancy in the next chapter), though since I'm only this far in, I don't know to what end. Perhaps to the same end as Tolkein's, which I suspect is that fate will unfold as it should as long as a company (not just an individual) is true.
However, the striking thing about the strategy in the battles referred to in this chapter is the utter lack of redundancy. If any one thing had gone wrong, there was no backup. Just a striking contrast I thought I'd comment on, I don't know if it means anything.
Also, tip-o-the-hat for your managing suspence and the pacing of revealations - it's just right. I don't know too much more or too much less than the characters.