Battle of Isengard
From Tolkien Gateway
The Battle of Isengard was a battle fought during the War of the Ring.
The assault was carried out by the Ents, Huorns and the two Hobbits, Merry Brandybuck and Pippin Took who attacked from Fangorn Forest. The defenders of Isengard were Orcs led by Saruman. The attackers surrounded Isengard, destroyed its gates, crumbled its walls and broke the dam, which flooded the Ring of Orthanc, and the pits that Saruman used to create his war machines.
The casualties were, at least one Ent for the attackers, and the entire force of Orcs that defended Isengard, which may have been around one or two thousand.
In the end, the Ents took over Isengard and made it one of the most beautiful places in all of Middle-earth.