Wainriders

The Wainriders were a confederation of Easterling tribes who were united by their hate of Gondor, fueled by the dark lord Sauron. Following the Great Plague which weakened Gondor, they started their attacks in 1856 (T.A.), defeating the Gondorian army and killing king Narmacil II. They rode in great wagons and chariots (which gave them their name), and raided the lands of Rhovanion, destroying or enslaving its people. Gondor gradually lost all of its possessions east of Anduin to them. The thirtieth king of Gondor, Calimehtar son of Narmacil, defeated the Wainriders at the Field of Celebrant, buying some rest for his land. However the Wainriders struck back in 1944, allying themselves with the Haradrim of Near Harad and the Variags of Khand. They managed to kill king Ondoher and all his heirs, but instead of riding on to Minas Anor and taking the city, they paused to celebrate. Meanwhile, general Eärnil of Gondor's southern army had defeated the Haradrim and rode north to defend his king. He came too late to rescue Ondoher, but managed to totally defeat the Wainriders. Eärnil was crowned king. After this defeat the might of the Wainriders was broken, and they retreated east. They still held Rhovanion, but never troubled Gondor again. It later turned out that their attacks were staged by Sauron to allow him to reclaim Mordor while Gondor's watch was diverted.