Fighting barbarians makes barbarians
A war against a supposed savage enemy changes the people waging it more than the enemy. The torture and cruelty used to defend civilization turn its defenders into the very barbarians they claim to fear.
Power needs an imagined threat
A regime out of touch with its own people can prove its strength by inflating even a faint, imaginary sign of outside danger into an emergency. The enemy is created, not discovered, and can be found anywhere a state needs one.
Empire's strength is shared complicity
An oppressive system lasts by drawing ordinary, reasonable people into its wrongs, so that even a decent official finds his comfortable post depends on the cruelty he dislikes. Being a person of peace and reason does not exempt you from the system you serve.
Sympathy can also imprison
Caring for someone who has been harmed can still hold them captive, because the helper keeps the power to define and keep them. Compassion offered from a position of power is not free of that power.
Protest turns insiders into enemies
When an official objects to how the state treats its captives, the state can reclassify him as a traitor and subject him to the same treatment. Only on the receiving end of that violence does he fully understand what he had overseen.