Summary by Lewis G. Miller
Although titled “How the Strength of All Principalities Should Be Measured” (depending on your translation), the chapter primarily concerns itself with advice for those Princes who take charge of weak states. Machiavelli gives some insight into what this weakness might involve, such as a lack of men or wealth, and how we can deal with this.
For this chapter we thought it appropriate to discuss this partly in reference to the idea of deterrence. He argues that if you are weak, you are likely to take a defensive approach to international affairs. Looking to the small states of the Holy Roman Empire, Machiavelli thought that these were able to remain independent because they were so well fortified, their soldiery well-organised, and their Princes well loved. As a result, he concludes that it is sensible for a Prince to increase the costs of any attack on your city.
The chapter also has an interesting insight into how Machiavelli sees human nature. He argues at one point that those under siege will not take their anger out on the Prince, but defend him more loyally as they have sacrificed so much already in his defence.