Niccolo Machiavelli's The Prince is a handbook for how leaders should govern in order that both the ruler and the state should survive. It can be considered one of the most important books ever written, as it continues to be studied widely at the university level and is used as a guide by political and corporate leaders for lessons on how to treat subordinates or subjects and for how to ensure the survival of the ruling individual or clan.
Machiavelli studied leadership qualities very closely, an interesting task given the influence of the Medici during his time. One of his lessons emanated from instances in which rulers, or princes, unnecessarily undermined their legitimacy in the eyes of those they ruled by disarming them. One could have thought that disarming one's subjects would make the personal survival of the ruler more secure. Machiavelli suggested otherwise, postulating that, rather than disarming subjects, and consequently making them less loyal, princes should provide weapons to their subjects. In so doing, the subjects would feel greater loyalty to both the prince and to the state, and, being armed, they would be more likely to come to the physical defense of the state were it attacked.
In this way, Machiavelli was doing what most strategists, advisers, historians and others do: learn from the mistakes of the past so that future generations need not repeat them.