Return of the King Book 5, Chapter 10
Merry and Bergil watch the army leave for Mordor. It presses on through Osgillath and into the gloom of the crossroads. Aragorn announces that Gondor has returned and then they move forward toward the main gates of Mordor. Throughout the third day, they travel onward announcing to the surrounding lands that they are free of Sauron's control. A sortie of men and orcs attacks but they defeat them easily. Aragorn knows that this was a ploy to distract them or slow them down. Legolas can see the Nazgul pacing them far above. When they come close to the gates, some men are overwhelmed and Aragorn allows them to leave. They approach the black gates with fewer than six thousand men.
When they reach the gate, it is evident that the two great hills on either side are hiding armies of the dark lord. The armies of Gondor are protected by either hill and Aragorn rides forward with Eomer, Imrahil, Gandalf and Pippin. A messenger comes forward and offers them Frodo's mithril coat and his cloak. The messenger tells them that Sauron demands that they retreat to Gondor and pay him tribute to return Frodo alive. Gandalf asks the messenger how Sauron could expect one prisoner to be worth so much. He takes the mithril coat and cloak from him but says that there will be no retreat. The messenger lets loose a hideous cry and the gates of Mordor crash open. Armies come from behind the hills and pour from the gate. The men of Gondor leap to battle. Pippin prepares to die as he draws his sword. The swarms of orcs break like a storm on the ranks of Gondor. A great orc falls over Pippin and as he passes out he thinks he hears men yelling about eagles.
"For one moment more Pippin's thought hovered. 'Bilbo!' it said. 'But no! That came in his tale, long long ago. This is my tale, and it is ended now. Good-bye!' And his thought fled far away and his eyes saw no more." Book 5, Chapter 10, pg. 187