The Wealth of Nations by Part 5 Chapter 2 Page 13

War and the preparation for war are the two circumstances which in modern times occasion the greater part of the necessary expense of all great states. But in the ancient republics of Greece and Italy every citizen was a soldier, who both served and prepared himself for service at his own expense. Neither of those two circumstances, therefore, could occasion any very considerable expense to the state. The rent of a very moderate landed estate might be fully sufficient for defraying all the other necessary expenses of government.

In the ancient monarchies of Europe, the manners and customs of the times sufficiently Prepared the great body of the people for war; and when they took the field, they were, by the condition of their feudal tenures, to be maintained either at their own expense, or at that of their immediate lords,