Machiavelli describes three ways to hold states that have
been accustomed to living freely under their own laws. The first
is to devastate them. The second is for the conqueror to occupy
them. The third is to allow the state to maintain its own laws,
but to charge taxes and establish an oligarchy to keep the state
friendly. The third option is advantageous because the newly imposed
oligarchy will work hard to secure the authority of the conquering
prince within the conquered state because it owes its existence
to the prince and cannot survive without his support. Thus, as long
as the goal is not to devastate the other state, it is easiest to
rule it through the use of its own citizens.
Hope this helps, took me awhile to type it all. :)
