A civil war erupted when Eärendur finally died. Amlaith, however, failed to overcome his two brothers and founded the kingdom of Arthedain. (His brothers founded the kingdoms of Cardolan and Rhudaur).
His reign in Arthedain was largely a peaceful one, although border disputes with the realms of Cardolan and Rhudaur never fully ceased. Under his rule the capital was formally removed from Annúminas to Fornost.
He was succeeded at his death in 946 T.A. by his son Beleg.