Answer:
Euphemism that ¨backfires¨ and produces irony.
Explanation
The Pacification of the Primitive Tribes of the Lower Niger
is a euphemism for using whatever force it takes to control and suppress other peoples. It backfires because the same word Pacification is used to describe a violent (non-pacific) event, by the same people who are supposed to be pacified by force, that lead surprisingly to for the moment the spirit of the clan was pacified.