The Lord of the Rings: The Return of the King | The Battle of Dale (Animated Documentary)

The Battle of Dale was a battle fought between the Kingdom of Dale allied with the Dwarves of Erebor and the Iron Hills, against the Easterlings of Rhûn in the valley of Dale during the War of the Ring in the late Third Age, and was the decisive battle in the Northern Theater of the War of the Ring. The Easterlings were initially successful, driving the Dwarves and Men of Dale back and besieging them for several days, but were later routed.
The battle was very important for the future of Middle-earth. Though it could not change the outcome of the War of the Ring, which was tied to fate of the One Ring, a victory by Sauron's forces would have had devastating consequences.
The Battle of Dale is not directly featured in the The Lord of the Rings film trilogy. However, in the Extended Edition of The Return of the King (that's why it's in the title), Legolas tells Gimli that he fears that war is already marching upon their own lands. This was described by Peter Jackson to refer to the Battle of Dale and the attacks on the Woodland Realm.