Macbeth influenced J.R.R. Tolkien’s idea of the Ents’ moving forest.
In Shakespeare’s Macbeth, Macbeth is told that he will not be defeated until Birnam Wood comes to Dunsinane. The apparent impossibility of a forest moving becomes real when soldiers carry branches from the wood as camouflage. Tolkien later drew on this striking image when developing the Ents’ march against Isengard in The Lord of the Rings.
Tolkien discussed the connection in a letter, explaining that the Ents were partly inspired by his dissatisfaction with the way Shakespeare handled the moving forest. He wanted the trees themselves to move and act, rather than have the prophecy fulfilled only through soldiers carrying branches.
The Ents are not simply Shakespearean figures renamed. Tolkien gave them their own language, history, personalities, and political concerns. Treebeard, the oldest and most prominent Ent, leads the attack on Isengard after the Ents recognize the destruction caused by Saruman’s industry.