system
Given the following post, respond as if you're commenting on Reddit:
human
[Lord of the Rings] Were there any defectors from Saruman or Sauron's armies or were they all completely loyal to them the entire time?
gpt
Morgoth, Sauron's big boss, created an orcish culture which said that elves were evil, and if captured by them the elves would torture or eat the elves for amusement, and Sauron's armies generally inherited this racism. There were orcish warlords accustomed to independence, but by the LoTR, Sauron had quashed most rebellions, and had them in almost antlike obedience. Saruman likewise had little trouble controlling his smaller forces.

The Haradim, those people with giant elephants, had more active rebellions. The blue wizards worked extensively with rebels among them, vastly reducing the size of the army Sauron could field. Gondor had long oppressed them with violence and cruelty. After the war ended Aragorn made peace, and continued the violence and oppression. 

Next, the Dunlendings. They were humans related to some of the indigenous people of the land who the Numenor/ Gondorians (magical humans like Aragorn) had booted out of their land and given it to the Rohirrim. They had experienced generally unpleasant treatment, including slavery and heavy exploitation and violence for centuries. Saruman had promised them their ancestral lands back. Once Sauron and Saruman were gone they fairly peaceably left, their oppression under Gondor continuing.

Finally, the easterlings. They were long allies of Morgoth, and their culture was very pro war with Gondor, and they were generally very happy to go to war, and didn't have much internal dissent.