
In the last days of Beleriand Galadriel and her husband Celeborn had left Tol Sirion and Ossiriand towards Eriador to gather an army among the wild elves and men. They mostly found followers among the Nandor of Eriador and some wayward Avari clans of the Windan, Penni and Kindi and first pushed Morgoths comparatively weak hordes out of Eriador, making an alliance with tribes of wild men, notably the Beregrim or ancestors of the Forodrim or Downsmen and early ancestors of the Gwathuirim and later Branomaboi or Bree-folk while other men, such as the Bórian tribesmen of later Angmar and the Arvandor of Rhudaur allied swore fealty towards Morgoth.
With their unexpected success the Alliance also caught the attention of many of the Wood-elves of Greenwood and Lothlórien while the dwarves of Dúrin's folk supported them with troops as well as weapons and made an alliance with the Fell Folk of the East, ancestors of the Northmen. While they could free Eriador and Rhovanion and put the orcs northern advance to a halt a tribal alliance of men of darkness formed in the Southlands or Tarma-Pal while they engaged pushing forward to Beleriand, where they eventually joined with the host of the Valar near the end of the War of Wrath.With the fall of Beleriand they assisted the refugees of Balar to gather and reorganise and in the end also put an end to the dynasty of Tarma-Pal, occupying their terretory and leaving the remaining populance under the supervision of trusted rangers.In the aftermath the alliance disbanded, many of the elves acknowledging the high-kingship of Gil-Galad.The dwarves left the alliance angry due to feeling abandoned after the fail of the alliance to prevent the Sacking of Mount Gundabad of while the Northmen were pushed westwards by alliances of Uldorian Easterlings arriving on the shores of the Rhûnaer and sought alliance with the recently appeared Númenóreans, largely due to the work of the half-blood known as Tal-Elmar.
Many elves of the alliance later settled in Rivendell, Edhellond, or Lothlórien while the eriadorian tribesmen largely sought alliance with the Faithful und eventually were instrumental in the formation of Arnor.