To use a cliché, victory is snatched from the jaws of defeat before the gates of Minas Tirith. Aragorn's daring the Paths of the Dead allows his dramatic arrival to secure the field, but many people — not least Éowyn and Merry — join together to overcome the Enemy's overwhelming force. Denethor's madness provides a contrast to the heroic deeds on the field, an example of how pride and arrogance — his conviction of the hopelessness of the struggle — can destroy nobility and strength. Even Éowyn, who fights because she cannot bear her life, has turned despair into a weapon against the darkness, but Denethor allows it to master him.
Denethor goes mad because he puts faith in the visions of the palantír. Like Galadriel's mirror, the seeing stones can show the future, but such glimpses are difficult to interpret. Denethor assumes the black ships carry enemies, and he falls into despair — in fact, they carry friends. When Aragorn reveals himself to the Orthanc-stone, Sauron assumes that Isildur's heir has the Ring, and the Enemy attacks — in fact, Aragorn wants to distract Sauron from Frodo's quest. These misinterpretations imply that knowing the future does not insure correct decisions, but may even hinder them.
When the Armies of the West set out for Mordor, they again act in the face of despair, without certain knowledge of the outcome. Although these are the traditional heroes of epic story, the warriors, kings, and wizards, they realize that their actions cannot directly win the war with Sauron — they can only hope to give the Ringbearer his chance. While Tolkien clearly admires their heroism, the true hero is a small hobbit, struggling alone to complete his task.
