Battle of Dagorlad

The Battle of Dagorlad was a great battle fought at the end of the Second Age between the Last Alliance of Elves and Men and the forces of Sauron, upon the barren plain before the gates of Mordor. It was one of the largest battles ever fought in Middle-earth and a decisive victory that opened the way for the siege of Barad-dûr.

Background

After the Downfall of Númenor, Sauron returned to Mordor and again made war upon the free peoples. In answer, Gil-galad, High King of the Noldor, and Elendil, lord of the Dúnedain of the realms in exile, formed the Last Alliance and marshalled a vast host of Elves and Men. Marching east, they came to the plain of Dagorlad, "the Battle Plain", that lay before the Black Gate of Mordor.

The Battle

There the host of the Alliance met the full strength of Sauron. The battle was vast and grievous, and the Alliance was victorious, though at great cost. All living things, it was said, were divided in that day, and even some Elves and Men fought on the side of Sauron. Many fell, and the marshes that later spread over part of that plain, the Dead Marshes, were held to hold the faces of the dead who perished there.

Aftermath

Having broken Sauron's army at Dagorlad, the host of the Alliance passed into Mordor and laid siege to the Dark Tower of Barad-dûr, a siege that lasted seven years. It ended only when Sauron came forth in person and was overthrown upon the slopes of Mount Doom, where Gil-galad and Elendil were slain and Isildur cut the One Ring from Sauron's hand.