The Dead Marshes were reeking wetlands that lay northwest of the Dagorlad and southeast of the Emyn Muil. They may have been an extension of the Nindalf although the two swampy areas are separately named and seem to be disconnected on maps of the region. The marshes were an endless network of pools and soft mires filled with water-courses, and in the dark waters could be seen the dead from battles of long ago.
In the year S.A. 3434 the host of the Last Alliance of Elves and Men fought the forces of Mordor in the Battle of Dagorlad. During the battle on the plains more than half of the Elves of Lórien under the command of King Amdír were driven into the Dead Marshes. After the battle many of the slain were buried outside of the marshy area but over time (in the Third Age) the Marshes had grown and swallowed the graves.
In T.A. 1944 King Ondoher of Gondor was caught by a surprise attack by the Wainriders upon the Dagorlad. When the King and his guard were destroyed many of the confused soldiers of Gondor were driven by the attackers into the Dead Marshes. However, after Eärnil II won the Battle of the Camp, those of the Wainriders who were not slain in the fight were themselves driven into the Dead Marshes and there perished.
After Frodo and Sam had captured Gollum in the Emyn Muil (on 29 March 3019), he revealed that he had found a hidden way across the Marshes. The three took Gollum’s passage, where they saw candles and lights dancing about. Frodo was mesmerized by the lights and tried to reach out and touch the faces of the dead, at the bottom of the marshes. Gollum told them that the dead could not be touched, suggesting that he had once tried to eat them.
In The Letters of J.R.R. Tolkien, Tolkien speculated that the description of the Dead Marshes may have been based on his personal experience in World War I, specifically, the Battle of the Somme. When it rained, blast craters in no-man's land would become a series of pools or lakes with bodies of dead soldiers, from both sides, floating in them.
 See also
- ↑ J.R.R. Tolkien, The Lord of the Rings, The Return of the King, "Map of Rohan, Gondor, and Mordor"
- ↑ 2.0 2.1 2.2 J.R.R. Tolkien, The Lord of the Rings, The Two Towers, "The Passage of the Marshes"
- ↑ J.R.R. Tolkien, The Lord of the Rings, Appendix B, "The Second Age"
- ↑ J.R.R. Tolkien, Christopher Tolkien (ed.), Unfinished Tales, "The History of Galadriel and Celeborn", "Appendix B: The Sindarin Princes of the Silvan Elves"
- ↑ J.R.R. Tolkien, Christopher Tolkien (ed.), Unfinished Tales, "Cirion and Eorl and the Friendship of Gondor and Rohan", (i) The Northmen and the Wainriders
- ↑ J.R.R. Tolkien, The Lord of the Rings, Appendix B, "The Third Age"
- ↑ 7.0 7.1 J.R.R. Tolkien, The Lord of the Rings, Appendix B, "The Great Years"
- ↑ J.R.R. Tolkien, The Lord of the Rings, The Fellowship of the Ring, "The Council of Elrond"
- ↑ J.R.R. Tolkien, The Lord of the Rings, The Two Towers, "The Taming of Sméagol"
- ↑ J.R.R. Tolkien; Humphrey Carpenter, Christopher Tolkien (eds.), The Letters of J.R.R. Tolkien, Letter 226, (dated 31 December 1960)