Herbert Spencer notes that traditionally the growth in government revenue has come about because of war (1882)

In his under-appreciated work The Principles of Sociology (1874-1896) Spencer in Book V “Political Institutions” gives a detailed sociological and historical account of how the institutions which compromise the modern state first appeared and grew into the structures he saw around him in the late 19th century. As was common at the time, he realised that the key institutions emerged slowly through a process of violence and power-sharing with other groups. In this chapter on “Revenue” he notes that external conquest has two sides to it - on the one hand the conquest of others and the confiscation of their property increases the revenue of the state, but on the other hand the leader or king also turns upon his own subjects and loots them in turn, either by conscripting them into the army or taxing them to help pay for the army. His rather sad conclusion is “But to the last as at first, and under free governments as under despotic ones, war continues to be the usual reason for imposing new taxes or increasing old ones.”