I want to make a homebrew dnd one shot in the world of lotr (most paid modules are whole campaigns)

My idea would be the prelude to the final battle of sauron during the siege of barad-dur.

The players will have to sneak into the enemy camp and get recognized enough by the soldiers that they listen to them.

They will spread the idea of striking back at the besiegers and during this counter attack either Sabotage or fight saurons forces so that he can be slain.

What are your thoughts on this and what parts of the simarilion should I reread beforehand