In Chapter III, Machiavelli seems to think we can learn something from the example of Louis XII, who lost Italy twice. What are these lessons?
If the annexed state has the same language and customs, you simply kill the prince and extinguish his bloodline. If the annexed state has a different language and similar customs, you simply kill the prince and keep prior laws and taxes. If they have a different language and customs, you need to go there in person so they learn to love or fear you, or to send colonies to strategic points in the country so you do not need to send armies.
In every case, however, one should do all harm that is necessary at the beginning so that over time you seem to be good. One should weaken neighboring powers so that those displaced do not have allies to find. In addition and related, one should either pamper men or eliminate them, because the dead cannot seek revenge.
This is part of planning ahead, that is, one should always think ahead and provide for future disorders, including war, which should not be avoided but waged when you need to.