Thousands of years before the events of the novel, the Dark Lord Sauron had forged the One Ring to rule the other Rings of Power and corrupt those who wear them: the leaders of Men, Elves and Dwarves. He was later vanquished in battle by an alliance of Elves and Men led by Elendil and Gil-galad. Isildur, a ruler of Men, cut the One Ring from Sauron's finger, claiming it as an heirloom for his line, and Sauron lost his physical form. When Isildur was later ambushed and killed by Orcs, the Ring was lost in the River Anduin at Gladden Fields.
Over two thousand years later, the Ring was found by one of the river-folk called Déagol. His friend[11] Sméagol immediately fell under the Ring's influence and strangled Déagol to acquire it. Sméagol was banished and hid under the Misty Mountains, where the Ring extended his lifespan and transformed him over the course of hundreds of years into a twisted, corrupted creature called Gollum. He lost the Ring, his "precious", and, as recounted in The Hobbit, Bilbo Baggins found it. Meanwhile, Sauron re-assumed physical form and took back his old realm of Mordor. Gollum set out in search of the Ring, but was captured by Sauron, who learnt from him that "Baggins" in the Shire had taken it. Gollum was set loose, and Sauron, who needed the Ring to regain his full power, sent forth his powerful servants, the Nazgûl, to seize it.