War between Sauron and an alliance of Elves and Men at the end of the Second Age. The war was fought in and around Mordor between 3434 and 3441 of the Second Age. In the end Sauron was defeated and the One Ring was taken from him, but since the Ring was not destroyed Sauron was able to rise to power again in the Third Age. The Last Alliance of Elves and Men:
The Last Alliance of Elves and Men was formed in 3430 by Gil-galad, the High King of the Noldor, and Elendil, the High King of Gondor and Arnor. They united to oppose Sauron, who had attacked and captured Minas Ithil - a stronghold of Gondor on the borders of Mordor - the year before in 3429. Sauron was angry that the survivors of Numenor had founded the Kingdom of Gondor near his realm, and he sought to destroy them.
Elendil's son Isildur escaped from Minas Ithil and fled to Arnor in the north where his father lived. Elendil's other son Anarion remained to defend Gondor. Anarion managed to hold Osgiliath and drive Sauron's forces back to Mordor for the time being, but he did not have sufficient strength to defeat Sauron.
Elendil took counsel with his friend and ally Gil-galad, and they realized that their races needed to unite against Sauron or all of Middle-earth would be in danger. Gil-galad set out with an army of Elves from Lindon, along with Cirdan from the Grey Havens. Elendil gathered an army of Men of Arnor and awaited Gil-galad in the Tower of Amon Sul on Weathertop. Together they traveled to Rivendell, the home of Elrond, who was to act as Gil-galad's herald and commander on the battlefield.
In 3431, a great host of Elves and Men was assembled at Rivendell, the likes of which was never seen again in Middle-earth. The army of the Last Alliance set out for Mordor, crossing the Misty Mountains in 3434 and marching down the Anduin. They were joined by Elves of Lothlorien led by Amdir and Elves of Greenwood the Great led by Oropher and his son Thranduil. Some Dwarves of Durin's line from Khazad-dum as well as a small number of Dwarves from other houses also joined them.
South of Greenwood the Great, the army of the Last Alliance found that the gardens that the Entwives had tended there had been destroyed. Sauron had burned the gardens in a scorched earth policy in order to prevent the Last Alliance from replenishing their supplies with the Entwives' crops. The army continued south through the desolate Brown Lands to Mordor.
The Battle of Dagorlad:
In 3434, the armies of the Last Alliance and Sauron met in battle outside the Black Gate of Mordor on the great plain that became known as Dagorlad, the Battle Plain. The army of the Last Alliance consisted of the forces that had marched from the north and the Men of Gondor who had been defending their borders.
However, the Men who lived in the White Mountains did not heed the call to battle despite an oath they had sworn to Isildur to oppose Sauron. These Men of the Mountains were cursed as Oathbreakers by Isildur and were condemned to haunt the Paths of the Dead.
Sauron's forces consisted mainly of Orcs and Men. Many of the Men who fought for Sauron came from the lands of Rhun in the East and Harad in the South. There were also some Men of Numenor who had been corrupted by Sauron and were called Black Numenoreans. Two of these Black Numenoreans named Herumor and Fuinur had become lords among the Haradrim and led their people into battle against Elendil and Gil-galad.
A small number of Dwarves fought on Sauron's side, though none from Durin's line. Sauron also had at his command Trolls and other creatures as well as his deadliest servants, the Nazgul.
When the battle began, Oropher of Greenwood the Great did not wait for Gil-galad's signal and charged heedlessly forward to his death. The Elves of Lorien led by Amdir also fared poorly. They were cut off from their allies and were driven into the the marshland to the south, where Amdir and more than half his troops were killed. This marshland became known as the Dead Marshes because of the corpses of Elves, Men, and Orcs that lay there after the War of the Last Alliance.
But the main forces led by Elendil and Gil-galad were victorious against Sauron in the Battle of Dagorlad. The enemy forces feared Aeglos, the spear of Gil-galad, and Narsil, the sword of Elendil, and they could not withstand the united front of the Elves and Men of the Last Alliance. Sauron retreated to Mordor and barricaded himself in Barad-dur, the Dark Tower.
The Siege of Barad-dur:
The Siege of Barad-dur lasted for seven years, from 3434 to 3441. The army of the Last Alliance entered Mordor and surrounded the Dark Tower, but they could not break its defenses. Isildur sent his sons Aratan and Ciryon to Minas Ithil to guard against any attempt by Sauron to escape by way of Cirith Ungol. Isildur's eldest son Elendur remained at his side throughout the war.
Sauron sent out many sorties from the tower and he also attacked the siege army from above with fire and with arrows and other projectiles. Many Elves and Men were killed. Anarion died in 3440, his helmet crushed by a stone thrown from Barad-dur.
Finally in 3441, Sauron came down from his tower in an attempt to break the siege. He made his way to Mount Doom, where he was confronted by Gil-galad and Elendil. The three fought on the slopes of Mount Doom until all of them fell. Gil-galad was burned to death by the heat of Sauron's hand, and as Elendil died his sword Narsil broke beneath him.
Sauron's physical body was also cast down. Isildur cut the One Ring from Sauron's hand with the hilt-shard of Narsil. Elrond and Cirdan advised him to destroy it immediately in the fires of Mount Doom, but Isildur refused and kept the Ring for himself. Because the Ring which contained much of his power remained, Sauron's spirit survived.
After the War:
Although the war ended in victory for the Last Alliance, the defeat of Sauron was not complete. He fled to the East where he rebuilt his strength over the centuries. The Nazgul also went into hiding, awaiting their master's return to power. Many of the Men who had been allied with Sauron returned to their homelands and remained enemies of Gondor and Arnor. Barad-dur was destroyed but its foundations, which had been strengthened with the power of the One Ring, stood intact.
The Elves and Men of the Last Alliance suffered great losses in the war. More than half of the forces from Lothlorien and two-thirds of the forces from Greenwood had perished. A remnant of the Elves of Lindon returned with Cirdan to dwell at the Grey Havens.
Isildur was killed just two years after the war by a band of Orcs in the Gladden Fields, and the One Ring was lost in the waters. The population of Arnor had been greatly diminished, and the North-kingdom declined and eventually ended after a war with the Lord of the Nazgul. Gondor's losses were less grievous, but it was not long before they too were under attack by Sauron's minions.
By the end of the Third Age, Sauron had regained much of his power and returned to Mordor. It was not until the One Ring was finally destroyed on March 25, 3019, that Sauron was utterly defeated.
Names & Etymology:
The Last Alliance was so called because it was the last time Elves and Men came together in great force for a common purpose. The two races became estranged during the Third Age, and although a number of Elves aided the Fellowship and fought to defend their own realms during the War of the Ring they did not form a united front with Men against Sauron as they had during the Last Alliance.
The Battle of Dagorlad was fought on the plain in front of the Black Gate which came to be called Dagorlad, or the Battle Plain, from dagor meaning "battle" and lad meaning "plain."
Sources:
The Fellowship of the Ring: "The Shadow of the Past," p. 61; "A Knife in the Dark," p. 197-98, 203; "The Council of Elrond," p. 255-57
The Two Towers: "The Passage of the Marshes," p. 234-35
The Return of the King: "The Passing of the Grey Company," p. 55; "The Tower of Cirith Ungol," p. 176
Appendix A of The Lord of the Rings: "Annals of the Kings and Rulers," p. 317-18; "The North-kindgom and the Dunedain," p. 323 note 1
Appendix B of The Lord of the Rings: "The Tale of Years," p. 365
The Silmarillion: "Of the Rings of Power and the Third Age," p. 290-95, 298; "Appendix - Elements in Quenya and Sindarin Names," entries for dagor and lad
Unfinished Tales: "The History of Galadriel and Celeborn," p. 243-45, 258; "The Disaster of the Gladden Fields," p. 273, 278-79 note 7, 279-80 note 11, 282 note 20; "The Istari," p. 395
The Letters of J.R.R. Tolkien: Letter #144
