During the War of the Ring the strange forest giants called Ents came in battle against the Orcs and Men of Isengard. Half Men, half trees, the Ents were fourteen feet tall, and the eldest had lived in Middle-earth for nine Ages of Stars and Sun.

Lord of the Ents was Fangorn who in the common toungue was called Treebeard. He was huge and ancient, for he belonged to the tallest and strongest race born into the World. Like oak or beech was the huge rough-barked trunk of Treebeard, while his branch-like arms were smooth and his seven-fingered hands were gnarled. Treebeard's peculiar, almost neckless head was tall and thick as his trunk. His brown eyes were large and wise and seemed to glint with a green light. His wild gray beard was like a thatch of twigs and moss. He was made of the fiber of trees, yet he moved swiftly on unbending legs with feet like living roots, swaying and stretching like long-legged wading birds.

Elvish histories tell how, when Varda, Queen of the Heavens, rekindled the Stars the Elves awoke, the Ents also awoke in the Great Forests of Arda. They came from the thoughts of Yavanna, Queen of the Earth, and were her shepherds of trees. Shepherds and guardians they proved to be, for if roused to anger Entish wrath was terrible and they could crush stone and steel with their hands alone. Justly they were feared, but they were also gentle and wise. They loved the trees and all the Elves and guarded them from evil. At the time of their awakening Ents could not speak, but the Elves taught them that art, and they loved it greatly. They delighted in learning many tongues, even the short chirping language of Men. Dearest of all they loved the language they had devised themselves, that none but Ents ever mastered. It rolled deep and full from their tongues as slow thunder or the timeless booming of waves on forgotten shores. In the slow passing of Entish time they formed their thoughts in unhurried meditation, and framed them into speech as undisturbed and rolling as the changing seasons.

Though Ents at times had great gatherings called Entmoots, for the most part they were a solitary folk living apart from one another in isolated Ent houses in the great forests. Often these were mountain caverns plentifully supplied with spring water and surrounded by beautiful trees. In these places they took their meals, not solid food but clear liquid stored in great stone jars. These were Ent-draughts and the magical fluid glowed with gold and green light. And in their Ent houses they took their rest, often finding refreshment in standing beneath the crystal coolness of a waterfall throughout the night. So the Ents lived out their wise, almost immortal lives, and the many races of the Earth thrived and declined around them without troubling their greatness.

Only when the foul Orcs came armed with weapons of steel were the Ents roused in wrath. The dwarves too were not loved by the Ents, for they were axe-bearers and hewers of wood. And it is said that in the First Age of Sun the Dwarf-warriors of Nogrod, who had sacked the Grey-elven citadel of Menegroth, were caught by Ents and utterly destroyed. Ents, in the years of starlight, had been both male and female, yet in the Ages of Sun the Entwives became enamoured of the open lands where they might tend the lesser Olvar - the fruit trees, shrubs, flowers, grasses and grains, whereas the male Ents loved the trees of the forests. So it was that the Entwives went to the open Brown lands, where they were worshipped by the race of Men who learned from them the art of tending the fruits of the Earth. Yet before the Second Age of Sun, the gardens of the Entwives were destroyed, and with the gardens went the Entwives. Among them was the spouse of Treebeard, Fimbrethil, who was called Wandlimb the Lightfooted. No tale tells of their fate. Perhaps the Entwives went to the South or East; but, wherever it was, it was beyond the knowledge of the Ents of the forests, who wandered in search of them for many long years.

So, though Ents could not die in the manner of Men, they became a dwindling race none the less. They were never numerous, and some were slain with steel and fire, and no new Entings came with the departure of the Entwives. As well, the vast forests of Eriador where many once roamed had by the Third Age been hewn down or burnt, so Only the Old Forest, which bordered the Shire, and the great Entwood of Treebeard remained. By the War of the Ring Treebeard was counted one of the three eldest Ents who had came forth under the Stars at the Time of Awakening. Besides Treebeard, there was Finglas, which means "leaflock", and Fladrif, which means "skin-bark", but the latter two had withdrawn even from the affairs of the Ents. Finglas had retreated in Ent fashion into the nature of his being and had become "treeish". He moved but little and few could tell him from the trees. Faladrif had battled alone against Orcs, who had captured his birch groves, slain many of his Entings, and had wounded him with axes. He eventually fled to live alone on high mountain slopes.

Though only Treebeard of the elders remained limb-lithe and active, there were many young Ents. Throughout the Entwood there was discontent because the Ents were being harassed by the servants of Saruman, who inhabited neighboring Isengard. So the Ents entered the War of the Ring, and this was the Great March of the Ents. Rank upon Rank of Ents marched on the stronghold of Isengard. With them came the Huorns, the Tree-spirits whom the Ents commanded and whose strength was nearly as great as their own. The very walls of Isengard were torn down and destroyed by Entish wrath and the power of Saruman shattered. The Huorns advanced into the battle of the Hornburg like a great forest, and the Orc legions of Saruman was exterminated. After the War of the Ring, the Ents again lived on peacefully in the Entwood, yet they continued to wane, and the Fourth Age was believed to be their last.