Plato wrote that the first things tyrants do is bring in an army of foreigners to enforce their will. Aristotle did as well:

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.