The Simplified Wealth of Nations of Adam Smith, Book 5, Chapter 1a: Government Expenses -- Military

Chapter 1a: The Development of Militaries

Part 1: Defence Expenditures

0 The first duty of the sovereign is to protect society from the violence and invasion of other societies. 1 The hunting nation is the lowest and rudest state of society. 2 The shepherd nation is a more advanced society. 3 The ordinary life and  exercises of a Mongol or an Arab, prepare him for war.
4 An army of hunters can seldom exceed 200-300 men.   5 A nation of husbandmen is a more advanced state of society.   6 Agriculture requires a settlement even in its rudest and lowest state.
7 In a more advanced society, two causes render it impossible for those who take the field to maintain themselves at their own expence:
  1. The progress of manufactures
  2. The improvement in the art of war
  8 When a husbandman goes to war which starts after seed-time and ends before harvest, his revenue is not reduced with his work's interruption.   9 It becomes universally necessary for the public to maintain those who serve the public in war, at least while they are employed to do so when: Military service would have been very tedious and expensive for those who served in war.   10 Fewer people can go to war in a civilized society than one in a rude state.   11 The cost of an army was not considerable in any nation until long after it fell entirely on the sovereign.   12 The trade of a soldier was not a separate distinct trade.   13 The art of war is certainly the noblest of all arts.   14 A shepherd has much leisure.

Next: Chapter 1b: Militias