The Wealth of Nations by Part 5 Chapter 1 Page 1

Of the Expenses of the Sovereign or Commonwealth

1. Of the Expense of Defence

The first duty of the sovereign, that of protecting the society from the violence and invasion of other independent societies, can be performed only by means of a military force. But the expense both of preparing this military force in time of peace, and of employing it in time of war, is very different in the different states of society, in the different periods of improvement.

Among nations of hunters, the lowest and rudest state of society, such as we find it among the native tribes of North America, every man is a warrior as well as a hunter.

When he goes to war, either to defend his society or to revenge the injuries which have been done