Det var Saurons makt, intimt kopplat till ringen, som drev dem.
Här är den faktiska texten i boken som beskriver vad som händer med värden vid Black Gate under händelserna på Orodruin:
But the Nazgûl turned and fled, and vanished into Mordor’s shadows, hearing a sudden terrible call out of the Dark Tower; and even at that moment all the hosts of Mordor trembled, doubt clutched their hearts, their laughter failed, their hands shook and their limbs were loosed. The Power that drove them on and filled them with hate and fury was wavering, its will was removed from them; and now looking in the eyes of their enemies they saw a deadly light and were afraid.
-- The Return of the King, Part 2, Chapter 4: The Fields of Cormallen (emphasis mine)
Dessutom var händelsen så katastrofal att dess effekter var synliga från ett stort avstånd.
Then rising swiftly up, far above the Towers of the Black Gate, high above the mountains, a vast soaring darkness sprang into the sky, flickering with fire. The earth groaned and quaked. The Towers of the Teeth swayed, tottered, and fell down; the mighty rampart crumbled; the Black Gate was hurled in ruin; and from far away, now dim, now growing, now mounting to the clouds, there came a drumming rumble, a roar, a long echoing roll of ruinous noise.
‘The realm of Sauron is ended!’ said Gandalf. ‘The Ring-bearer has fulfilled his Quest.’ And as the Captains gazed south to the Land of Mordor, it seemed to them that, black against the pall of cloud, there rose a huge shape of shadow, impenetrable, lightning-crowned, filling all the sky. Enormous it reared above the world, and stretched out towards them a vast threatening hand, terrible but impotent: for even as it leaned over them, a great wind took it, and it was all blown away, and passed; and then a hush fell.
The Captains bowed their heads; and when they looked up again, behold! their enemies were flying and the power of Mordor was scattering like dust in the wind. As when death smites the swollen brooding thing that inhabits their crawling hill and holds them all in sway, ants will wander witless and purposeless and then feebly die, so the creatures of Sauron, orc or troll or beast spell-enslaved, ran hither and thither mindless; and some slew themselves, or cast themselves in pits, or fled wailing back to hide in holes and dark lightless places far from hope. But the Men of Rhûn and of Harad, Easterling and Southron, saw the ruin of their war and the great majesty and glory of the Captains of the West. And those that were deepest and longest in evil servitude, hating the West, and yet were men proud and bold, in their turn now gathered themselves for a last stand of desperate battle. But the most part fled eastward as they could; and some cast their weapons down and sued for mercy.
-- The Return of the King, Part 2, Chapter 4: The Fields of Cormallen (emphasis mine)