I didn't learn about any of this in school. Defense, like everything else is better left to private and independent providers rather than a monopoly as a monopoly will become too corrupt. Too many people think we need government to provide society with defense. Its out of fear and ignorance. Governments are very wasteful, inefficient and coercive especially when it comes to defense. But it has no incentive to be efficient and moral as its only concern is propagating itself. There is so much history that is deliberately left out in governmental schools for the purpose of mind control and enslavement. The ruling masters could never really care about us. The more dependent people become on government the more tyrannical government becomes. The right and means to defend person and property are key to freedom, prosperity, peace, and victory. It would be far easier to afford defense if not for taxes. Taxation is theft. Every individual has the right to keep the product of his or her labor and sell it to whoever they choose. Each individual has the right to defend person and property for with out it there is no freedom.
Merchant marines in our time are another good example of private defense though they are more geared for protecting international product delivery I think.