During the Ents' assault on Isengard, they destroyed the dams built by Saruman's minions and therefore flood the place. Following this the Ents intercept on The Wold a force of Orcs sent to invade Rohan, sending them fleeing.
After the War of the Ring, the Ents were gifted Nan Curunír by King Elessar in gratitude for their aid. They moved many of their trees there and the place became known as the Watchwood and the Treegarth of Orthanc.
