Defense, on the other hand, is what you do to respond to an aggressor who is attacking. Cullinane says that if your protection is good enough then you do not need defense. Defense involves violence and you want to avoid it if possible. So he advocates focusing on protection. As I have frequently heard Philip Jacobson argue, there are great incentives to avoid violent conflict.
War is costly.
If it starts each party tries to destroy the valuables of the other. War is a negative sum game. Whereas peace with free trade is a positive sum game. We can normally expect potential antagonists to be willing to invest heavily in avoiding war. For instance a private security company will emphasize restoring stolen loot to its owner, the customer.