These involved added police responsibilities and enlarged the temptations of his neighbors, both men and animals.
Later, his family becomes a tribe.

In combination the duties of protection for the common good take on a larger view.

The village, the walled city and the armed state naturally follow.

Each stage of communal growth reduces the number of men set apart for defence or police duty.

There is a corresponding increase in the common store of human possessions and human happinesses.
From states grow nations, then empires, until but a small fraction of the people is engaged in any way in aggressive or defensive warfare, or even police work or the determination or enforcement of laws of justice as between individuals, cities, states, or communities of any sort.
The individual club at the mouth of the cave protecting the family has become for England a surrounding line of steel ships; for the United States, of 100,000,000 people, a mere outline of a military defensive organization, to be filled in when needed.