Raziel thinks a moment and says; "Probally would work sometime and slow them down, but we either must do a massive killings and twisting but that would need army of spies itself. Also devils would eventually figure out how solve the problem and in lower ranks devils can find replacement, we need do something...more dramatic and unfixable situation to them cause them break up. In plainest view killing The Nine would be solution, especially devils cannot resist fight over who shall take the nine crowns and thrones which have lefted open and vacant and devils can fight over rulership long time and sight would be same like in war between demons ironically. Whitout strong willed leadership leadinig them devils would crumble into pieces and lose temporally organization value and would be easy to route them back to their naturall plane."