The guard of a legitimate king is composed of citizens: that of a tyrant is composed of foreigners.

It is a habit of tyrants never to like anyone who has a spirit of dignity and independence. The tyrant claims a monopoly of such qualities for himself; he feels that anybody who asserts a rival dignity, or acts with independence, is threatening his own superiority and the despotic power of his tyranny; he hates him accordingly as a subverter of his own authority. It is also a habit of tyrants to prefer the company of aliens to that of citizens at table and in society; citizens, they feel, are enemies, but aliens will offer no opposition. - Aristotle, Politics


Then the poor, deprived of their land, were no longer eager for military service and had few children, so that soon all Italy was bereft of freemen and filled with gangs of foreign slaves, through whom the rich cultivated their estates, having driven away the free citizens. - Plutarch, The Life of Tiberius Gracchus