system
Given the following post, respond as if you're commenting on Reddit:
human
[The Lord of the Rings] Let's say the Army of the Dead didn't have to leave after the Battle of Minas Tirith, would Aragorn have used them to completely obliterate Mordor? Did Sauron have anything to counter them?
gpt
In the movies, Aragorn had promised that he would release them from their oath after the fight. Breaking an oath in Middle-Earth can have dire consequences - the army of the dead were cursed for breaking their own vows, and Gollum was cast into the fire for breaking his oath to guide the hobbits without harming them.

If Aragorn had kept them in bondage, he would have paid for it. That payment could be his kingship. It could be victory in war with Mordor.

In the books, the army of the dead didn't physically harm the living. Instead, they drove the Corsairs from their ships in terror. Aragorn commandeered these ships to pick up reinforcements from Gondor's allies, arriving at Pelennor Field and flanking Suaron's forces from the rear. The army of the dead wouldn't be able to make much of a difference  in Mordor - beyond the Black Gate, Sauron's orcs would be far more afraid of him than some measly ghosts.