Question

And he who becomes master of a city accustomed to freedom and does not destroy it, may expect to be destroyed by it, for in rebellion it has always the watchword of liberty and its ancient privileges as a rallying point, which neither time nor benefits will ever cause it to forget. And whatever you may do or provide against, they never forget that name or their privileges unless they are disunited or dispersed, but at every chance they immediately rally to them, as Pisa after the hundred years she had been held in bondage by the Florentines.

–The Prince,
Niccolò Machiavelli

Why does Machiavelli mention Pisa at the end of the passage?

to acknowledge that liberty will always triumph in the end
to demonstrate that Pisa was patient in waiting to rebel
to prove that cities that are not destroyed will eventually rebel
to show that Florence successfully held Pisa for a hundred years

Answer 1

to prove that cities that are not destroyed will eventually rebel

Machiavelli cites Pisa as a historical example showing that a city long held in bondage (100 years under Florence) still rallied to its ancient privileges and rebelled, supporting his point that unconquered free cities tend to revolt.