While within the legion every trace of the previous civic and aristocratic classification thus disappeared, and the only distinctions henceforth occurring among the legionaries were purely military, accidental circumstances had some decades earlier given rise to a privileged division of the army alongside of the legions-- the bodyguard of the general.

Hitherto selected men from the allied contingents had formed the personal escort of the general; the employment of Roman legionaries, or even men voluntarily offering themselves, for personal service with him was at variance with the stern disciplinary obligations of the mighty commonwealth.

But when the Numantine war had reared an army demoralized beyond parallel, and Scipio Aemilianus, who was called to check the wild disorder, had not been able to prevail on the government to call entirely new troops under arms, he was at least allowed to form, in addition to a number of men whom the dependent kings and free cities outside of the Roman bounds placed at his disposal, a personal escort of 500 men composed of volunteer Roman burgesses (p.

230).

This cohort drawn partly from the better classes, partly from the humbler personal clients of the general, and hence called sometimes that of the friends, sometimes that of the headquarters (-praetoriani-), had the duty of serving in the latter (-praetorium-) in return for which it was exempt from camp and entrenching service and enjoyed higher pay and greater repute.
Political Significance of the Marian Military Reform This complete revolution in the constitution of the Roman army seems certainly in substance to have originated from purely military motives; and on the whole to have been not so much the work of an individual, least of all of a man of calculating ambition, as the remodelling which the force of circumstances enjoined in arrangements which had become untenable.