I found that I don’t have anything to say on an overall theme to this chapter, so I’ll just share a few observations.
Tolkien takes a very, very linear approach to splitting up the storyline among different characters. This chapter, we’re with Aragorn, same as the previous one. Next chapter we’ll be with Merry and Pippin, and we won’t revisit Frodo and Sam until Book II. The result is that this chapter, I am absolutely certain, is very different on a re-read than it is to someone who is unfamiliar with the chapter that follows it. From the dead orcs, to the fallen broach of one of the Hobbits’ Elven-cloaks, to the news that Éomer brought of their battle with the orc band, all of it is told strictly from the perspective of Aragorn, Legolas, and Gimli, who know nothing of what is happening to Merry and Pippin. Next chapter all of it (or at least most of it) gets explained, but for the moment it’s left a mystery.
This is the first time in the books that Saruman becomes a real presence. He was discussed during the Council of Elrond, and he was a factor the Fellowship had to consider on their journey, but he’s always been remote. Here, not so much. His will is acting upon Aragorn, Legolas, and Gimli, sapping their strength and their morale even as it bolsers that of the orcs. For all that he remains distant, his influence is palpable in this chapter. They’re entering his sphere of, if not control, at least influence, and they’re definitely aware of it.
The moment when Aragorn (having nearly let the Riders go past) stands up and shouts, “What news from the North, Riders of Rohan?” is, for reasons I can’t really articulate, one of my favorite moments in the entirety of LotR. I love the entire encounter, really.
An important change to Éomer’s character from book to movie, and one I do not like: Book-Éomer wasn’t riding in the northern reaches of Rohan because he’d been exiled. He’d heard word of the orc band, asked for (and was denied) permission to hunt them down, went anyway, and then returned to Edoras to accept judgement for his actions.
I want to end on a question for my fellow Tolkien-o-philes: do we know that the old man is Saruman? I know that Gandalf says it probably was, but do we actually know this? Do we know anything about what he was up to? I don’t recall anything else Tolkien said about it.