Whenever I see anything on the Thirty Years war, it is always mentioned that the soldiers fighting the war were mercenaries who were hired by the nobility to fight for them. They got paid by being allowed to loot as much of the countryside as they wish, resulting in endless horror stories about the devastation these armies brought to the people of the Holy Roman Empire. My question is, basically, what were these mercenary armies? Where did these armies come from? Did these armies just wait around for a war to break out so they can fight people? Were they commonly used during wars at the time? Was it a major profession for people to join these mercenary armies?
This is a somewhat common misconception about the Thirty Years War. While the bulk of the troops were what we would call mercenaries, this was not atypical for a early modern European state to have only a small standing army. The rudimentary administration of the early modern states meant that there was a certain logic to subcontracting out to specialists during times of war when ordinary militias and feudal levies were inadequate. These military entrepreneurs had contacts with the state and the fiscal resources to recruit an army. Generally speaking, most early modern states preferred to have their contractors hire foreign troops. The Spanish Army of Flanders in Belgium had half of its members recruited from outside the Low Countries. This minimized the chances of desertion and thus made it less imperative to have timely pay. Very few captains or entrepreneurs hired out their armies to the highest bidder, rather they worked within established networks of the states.
Recruits came from outliers of the general population; some volunteered out of desperation, others were impressed into service. The Spanish in particular were notorious for emptying Spanish prisons for recruits for the Low Countries. Despite this, military service could promise some rewards such as plunder, or even shelter and quartering within German cities. Soldiering was not as much of a career in the modern sense of the word. Most soldiers on garrison duty would engage in other trades and professions.
The Thirty Years' War has the disadvantage of being located before the expansion of the state and the normalization of standing armies. The Dutch and the Swedish in particular brought this innovation forward during the war itself. Gustavus Adolphus's troops had the beginnings of a standardized uniform and the Maurice of Nassau introduced systematic training regimen. However, even these armies had to rely upon private subcontractors during the high tempo of military operations.
After the Treaty of Westphalia, the issue of mercenary armies and their depredations became a topic for German nationalist historians, especially after German unification. This scholarship presented the mercenary armies as part of German's larger victimization. This bias made the mercenary component of mercenary armies appear to more sinister and minimized the actual logic behind relying upon subcontracting out for armies.
sources
Glete, Jan. War and the State in Early Modern Europe: Spain, the Dutch Republic, and Sweden As Fiscal-Military States, 1500-1660. London: Routledge, 2002.
Parker, Geoffrey, and Simon Adams. The Thirty Years' War. London: Routledge & Kegan Paul, 1984.
Wilson, Peter H. The Thirty Years War: Europe's Tragedy. Cambridge, Mass: Belknap Press of Harvard University Press, 2009.