Treebeard leads the attack on Isengard in J.R.R. Tolkien’s The Lord of the Rings.
Treebeard is an Ent, an ancient tree-like being who lives in Fangorn Forest. His Elvish name is Fangorn, which is also the name of the forest. Merry and Pippin meet him after fleeing from the Orcs, and their account of Saruman’s destruction of the natural world helps persuade him to act.
Treebeard calls an Ent gathering, or Entmoot, where the Ents decide to march against Isengard. Their assault destroys much of Saruman’s fortress and floods the surrounding area, demonstrating the power of the forest’s guardians.
Quickbeam is another named Ent and is easy to confuse with Treebeard. Quickbeam is younger and more impulsive, while Treebeard is the oldest and best-known Ent in the story. Bregalad is Quickbeam’s translated name, not a separate leader.