I'll start with a completely obvious statement: there are a lot of images and symbolism here. Horses, plants, cliffs...all of it. Still, to me, this poem seems more abstract than usual, descriptive but completely open to interpretation.

Personally, I see it as Wolfe's thoughts at dawn on the Plains of Abraham immediately before the battle-he can sense how the battle will end, and he's accepting its inevitability. A sort of premonition, maybe.