First nation states lacked the funds needed to maintain standing forces, so they tended to hire mercenaries to serve in their armies during wartime. Such mercenaries typically formed at the ends of periods of conflict, when men-at-arms were no longer needed by their respective governments. The veteran soldiers thus looked for other forms of employment, often becoming mercenaries. Free Companies would often specialize in forms of combat that required longer periods of training that was not available in the form of a mobilized militia.
As late as the 1650s, most troops were mercenaries. However, after the 17th century, most states invested in better disciplined and more politically reliable permanent troops.
For a time mercenaries became important as trainers and administrators, but soon these tasks were also taken by the state. The massive size of these armies required a large supporting force of administrators. The newly centralized states were forced to set up vast organized bureaucracies to manage these armies, which some historians argue is the basis of the modern bureaucratic state.
The combination of increased taxes and increased centralisation of government functions caused a series of revolts across Europe such as the Fronde in France and the English Civil War.
In many countries, the resolution of this conflict was the rise of absolute monarchy. Only in England and the Netherlands did representative government evolve as an alternative. From the late 17th century, states learned how to finance wars through long term low interest loans from national banking institutions. The first state to master this process was the Dutch Republic. This transformation in the armies of Europe had great social impact. The defense of the state now rested on the commoners, not on the aristocrats.
However, aristocrats continued to monopolise the officer corps of almost all early modern armies, including their high command. Moreover, popular revolts almost always failed unless they had the support and patronage of the noble or gentry classes. The new armies, because of their vast expense, were also dependent on taxation and the commercial classes who also began to demand a greater role in society. The great commercial powers of the Dutch and English matched much larger states in military might.
As any man could be quickly trained in the use of a musket, it became far easier to form massive armies. The inaccuracy of the weapons necessitated large groups of massed soldiers. This led to a rapid swelling of the size of armies. For the first time huge masses of the population could enter combat, rather than just the highly skilled professionals.
It has been argued that the drawing of men from across the nation into an organized corps helped breed national unity and patriotism, and during this period the modern notion of the nation state was born. However, this would only become apparent after the French Revolutionary Wars. At this time, the levée en masse and conscription would become the defining paradigm of modern warfare.
In Spain armies were recruited from all the Spanish European territories including Spain, Italy, Wallonia (Walloon Guards) and Germany. The French recruited some soldiers from Germany, Switzerland as well as from Piedmont. Britain recruited Hessian and Hanovrian troops until the late 18th century. Irish Catholics made careers for themselves in the armies of many Catholic European states.
Before then, however, most national armies were in fact composed of many nationalities
Prior to the English Civil War in England, the monarch maintained a personal bodyguard of Yeomen of the Guard and the Honourable Corps of Gentlemen at Arms, or “gentlemen pensioners”, and a few locally raised companies to garrison important places such as Berwick on Tweed or Portsmouth (or Calais before it was recaptured by France in 1558). The Spartan Army was one of the earliest known professional armies. Boys were sent to a barracks at the age of seven or eight to train for becoming a soldier.
