Sky Pirate Subjugation

The Sky Pirate Subjugation was the large scale annihilation of the Sky Pirates in Barsburg's bid to control the skies.

History leading up to conflict
In a manga chapter, Bastien said that the Sky Pirate Subjugation took place towards the end of the Raggs War.

Aftermath
It has been hinted that most, if not all, of Frau's childhood friends died as a result of the Sky Pirate Subjugation.