Machiavelli works to achieve his primary purpose to convince readers that a prince must ruin a conquered republic or live there by:
1. Explaining the roots of rebellion in conquered republics.
The best way to secure a state that has been formerly free is by complete destruction. If the prince does not make this decision, he will be in danger of being destroyed himself. No matter if the state was acquired long ago, rebellions, encouraged by the ideals of freedom and tradition, will always rise.
2. Contrasting the characteristics of principalities and republics.
Machiavelli explains that cities or provinces used to being governed by a prince are easier to conquer after the family has been taken down. Citizens of these states have always obeyed a ruler and never met a free way of life. Thus, it is less problematic for the new prince to mantain the power in such places.
On the other hand, in republics, a sense of hatred and vengeance against the new prince will persist, so, to avoid rebellions, the best choice would be to destroy the republic or to personally occupy the conquered state.
