Final answer:
Machiavelli's secondary purpose is to persuade readers that a conquering prince must destroy a republic to control it, as citizens will always cherish their former freedom.
Step-by-step explanation:
The secondary purpose of Machiavelli in writing this passage from The Prince is to persuade readers that a conquering prince must destroy a former republic if he hopes to hold it. Machiavelli argues that citizens of a city accustomed to freedom will forever harbor the spirit of liberty and the memory of their former independence. Therefore, a ruler must take decisive and often destructive actions to secure control, as partial measures will not erase the people's desire for their ancient privileges and freedom.