"War – what is it good for?" Although they want no part of this warring, what draws the Ents into the battle?
Answer The deforestation caused by Saruman's war effort
While Treebeard is guiding Merry and Pippin to Isengard, they are made audience to Saruman's army causing great destruction and deforestation. Of course, this would impact the Ents, and they do enter into the war, after all, storming Saruman's tower and trapping him there.
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