Oops!
I didn't comment on the very end of the sequence where Merry and Pippin, perched high upon Treebeard, look and see the Wizard's Vale. They note the smoke, and Treebeard blows the comment off, as he always sees smoke rising from Isengard these days. Guess that he thought that Saruman burned coal or oil or natural gas and that's where all of the smoke came from. The two Hobbits also see the Uruks marching towards Helm's Deep. I'm not sure how they know that the war is on, but that's minor. The scene ends with a very perplexed Pip looking at the black plague marching on.