The fictional Seperatist holdouts from Star Wars kinda reminded me of the real world Imperial Japanese military holdouts that existed after World War II for these five reasons....
1. Holding out for decades even up to the next few conflicts with some being unaware that the war was already over.
2. Being somewhat formed when the person sending the surrender signal was not speaking clearly on the radio or had to rush downstairs to meet his wife's spaceship on the landing platform.
3. Several joining guerrilla forces against a bigger enemy.
4. Some assuming that the surrender signal is a propaganda trick from the enemy.
5. Their weapons and technology withering down and starting to malfunction due to the passage of time.