That's Ent-ertainment

[Lalwendë]

A possible reason for the change to the Ents' decision to go to war may be that Jackson wanted to show the destruction of the forest and the effect that this would have on the Ents? In the books we know that Treebeard knows of this and that the Ents decide to march, while in the films they do not know, and do not decide to march. It could have been more difficult to show them as creatures which knew they were being attacked and yet had to hold a debate on whether to act; in the films they are shown to make a sudden discovery and be provoked into anger.