In The Lord of the Rings: The Return of the King, the Rohirrim ride to Minas Tirith’s aid.
The Rohirrim are the horse-warriors of Rohan, led by King Théoden. When Gondor calls for help through the beacons, Théoden gathers his riders and secretly leads them toward the besieged city. Their arrival at the Battle of the Pelennor Fields is one of the trilogy’s largest and most celebrated action sequences.
The charge temporarily breaks the forces of Mordor outside Minas Tirith. Théoden is fatally wounded during the battle, while Éomer takes command after his sister Éowyn defeats the Witch-king with Merry’s assistance. Aragorn later arrives with forces from the Paths of the Dead, but they are separate from the Rohirrim.
The Rohirrim are also called the Horse-lords of Rohan. Their friendship with Gondor is rooted in the historical alliance between the two kingdoms, although the films present the rescue as a hard-won military commitment.