In An Inquiry into the Nature and Causes of the Wealth of Nations, Adam Smith suggests that the invention of the gun had a major effect on economic development. At the end of Book V, Chapter i, part a, Smith argues that guns makes it easier for rich nations to defend their wealth against barbarous nations. Smith is thinking of the many occasions in history where an invading, or raiding army, takes economic wealth by force. Fire arms narrow the difference between a population where everyone is a soldier and has military capacity; a modern prosperous population where only a minority are soldiers and have military skill and even that minority may not be as strong and experienced as the members of a ‘barbarian’ army. Smith is thinking of events like the barbarian invasions of the western Roman Empire, or Genghis Khan’s victories with a nomad army over urban societies, or Vikings raiding early Medieval Europe. The gun reduces the level of skill and military aptitude necessary to succeed in war. It leads to the building of expensive forts designed to withstand explosions.
The greater ease with which prosperous nations can defend themselves against a violent loss of wealth, and maybe the loss of the infrastructure of wealth creation, increases the incentives to create wealth. This speeds up the development of wealth and the majority of the population emerging from poverty. That advantage of gun powder is a major reason for growing wealth as rich nations are sure of benefiting from industry and commerce.
Smith might have added that fire arms leads to things he is not happy with, such as colonialism. As he points out fire arms give rich nations the easy means to defeat poor nations, what he does not point is that this leads to colonialism with aspects Smith finds undesirable: the expense of administration, the subordination of free trade to monopolies granted to business with close relations to power.
It takes fire arms to make the state more secure, and therefore more able to establish law and order, and the provision of basic institutions in education, basic transport infrastructure and so on. Smith does not say so much above the possibility that the state will be more able to become despotic and corrupt. He might be thinking that this would undermine prosperity, which itself would undermine the raising of money. Wars between the Netherlands, or Britain on one side, France on the other side, in the 17th and 18 Century generally resulted in victory for Britain and Holland, at a time when Britain was much smaller in population that France, as Holland always has been. This was connected with the greater wealth of Britain and Holland. They were less militaristic-aristocratic societies in spirit, and more commercial. The commerce generated wealth to finance war, as did the financing of public debt through selling government bonds and paying interest on those bonds.
Prosperity and military strength feed off each other, though a commercial society gives less importance to the military than less developed nations. Ancient writers regarded wealth as subversive of military strength as it led to a greater interest in pursuing wealth than in fighting on behalf of the nation. Smith provides a counter-argument to the ancients, and deepens his defence of civil and commercial society.