Machiavelli warned about using mercenaries and the mischief they can cause.
Sun Tzu was also no fan of mercenaries.
Back in 2001/02 we should have used the Russians as mercs in Afghanistan. Told them to go in there, clear out the Taliban, and bring bin Laden’s head on a pike for $500 billion. Complete autonomy to complete the task. No media, and no questions asked. Get the job done, get the money. Stay if you want, or get out at your convenience.
So long they fight for free business and do not get a bailout, is fine with me. The welfarist mercenaries is who we got to worry about.