In a conflict between humans/aliens or even aliens/aliens/humans
Both sides will have a rational leader who is interested in peace and a closed minded, easy to anger second in command /military adviser/vice president etc who will baulk at the leader's attempt at peaceful resolution and demand he declares war on the other side immediately.
Then there'll be a brief misunderstanding and either the peaceful leader will wind up killed or perhaps the warmongering 2nd in command will have a wife/son/daughter who is caught in the crossfire, only hardening his views that the enemy is pure evil and must be destroyed.
After a lot of chasing and The Doctor espousing on both sides basic goodness there'll be another sacrifice from the other side later on, changing the 2nd's mind that maybe there is some good in these former enemies after all and perhaps they should give peace a chance.
Standard trope for Silurians, Draconians and all alien species that aren't Daleks or Cybermen tbh