"Mercenary and auxiliary troops are useless and dangerous. Mercenaries are “disunited, undisciplined, ambitious, and faithless.” Because their only motivation is monetary, they are generally not effective in battle and have low morale. Mercenary commanders are either skilled or unskilled. Unskilled commanders are worthless, but skilled commanders cannot be trusted to suppress their own ambition. It is far more preferable for a prince to command his own army."

-Machiavelli "The Prince"