Siege of Barad-dûr

When the Last Alliance marched on Mordor in the closing years of the Second Age, they won a great victory at the Battle of Dagorlad, forcing Sauron back into his Dark Tower. The armies of Gil-galad and Elendil then passed into Gorgoroth and besieged Barad-dûr itself, seeking to finally rid themselves of the threat of the Dark Lord.

The Siege of Barad-dûr was set in II 3434, and occupied the last seven years of the Second Age. Though Sauron was confined within his tower, he was not without power to harm his besiegers, and they endured barrages of deadly missiles, as well as regular sorties by the besieged forces. They took many casualties in these years, including Elendil's second son Anárion.

At last Sauron sought to lift the Siege by offering combat against the leaders of the opposing armies. On the slopes of Mount Doom, he fought with Gil-galad and Elendil, and slew both of them, but Sauron himself was destroyed in that combat, and his spirit passed away. At that time Elendil's surviving son Isildur took the One Ring from Sauron's hand, an act that would have grave consequences in the distant future.

With Sauron's body destroyed, the Last Alliance captured Barad-dûr and razed it to the ground (though its foundations, made through the power of the Ring, could not be destroyed). After that time, Mordor was deserted for many centuries; the land was so filled with corruption and dread that none could bear to dwell there, but the Gondorians ringed it with castles and guard-towers to hold it against any return of Sauron's followers. Those defences held long into the Third Age, but at last they were deserted, setting the scene for Sauron's ultimate return and the War of the Ring that brought the Third Age to a close, nearly three thousand years after the victorious Siege of Barad-dûr.