Just because it exists historically doesn't mean that it's not a radical idea. Although, if you want historical perspective on how terrible of an idea it is, M

Just because it exists historically doesn't mean that it's not a radical idea. Although, if you want historical perspective on how terrible of an idea it is, Machiavelli didn't mince words. I repeat, then, that of all kinds of troops, auxiliaries are the most dangerous; for the prince or republic that calls them to their assistance has no control or authority whatever over them, as that remains entirely with him who sends them. ... A prince or republic, then, should adopt any other course rather than bring auxiliaries into their state for its defence, especially when their reliance is wholly upon them; for any treaty or convention with the enemy, however hard the conditions, will be less hard to bear than the danger from auxiliaries. ... And in truth no more favourable opportunity could be presented to an ambitious prince or republic for seizing a city or province, than to be asked to send troops there to assist in its defence. And therefore any one whose ambition so far misleads him as to call in strangers to aid in his defence, or in an attack upon others, seeks to acquire that which he will not be able to hold, and which after acquiring will be easily taken from him.