Italy during the 14-15th century was a perfect storm for the widespread use of mercenaries. Firstly, during this time most of Italy was divided into small cities states such as Genoa, Milan, Florence and Pisa. Many of these states would have had a small amount of territory and population; for example according to Goldwaithe, the population of Florence in 1347 was only 90,000. However, these states were also extremely rich due to their trade with the Middle East. That combination of lack of manpower and abundance of money led to mercenaries being an attractive and widely used option.
Mercenaries in the Italian city states fulfilled numerous functions for the social structure. According to Murphy, many of the cities experienced factional strife as power was often exercised by one (appointed) person, such as the Dodge of Venice. The mercenaries could thus be used as a sort of police force, as they had no interest in the affairs of city, they would be willing to put down an uprising, and by eliminating the need for a civilian militia there would be less of a chance of armed revolt resulting from factional strife. They also filled the role of the professional army and they quickly became ubiquitous in Italian conflicts, for example, according to Machiavelli, during the war between Florence (and their Venitan allies) and Milan he noted that “None of the principal states” used their own troops, “submitt[ing] their forces to the direction of others” by the use of mercenaries. Finally the use of mercenaries served as an acceptable occupation for lesser or landless nobles, during the 15th century most of the mercenary forces were led by such nobles which helped prevent the strife that would occur if unlanded nobles were unhappy. Thus, mercenaries served a role as a stabilizing factor for society and as the professional army class of states that were too small to maintain one drawn form their own citizens.
Goldthwaite, Richard A. The Building of Renaissance Florence: An Economic and Social History. Baltimore: Johns Hopkins UP, 1980. Online.
Machiavelli, Niccolo. History of Florence and of the Affairs of Italy. Gutenburg Project. Web. 14 Nov. 2014.
Murphy, David, and Graham Turner. Condottiere, 1300-1500: Infamous Medieval Mercenaries. Oxford: Osprey, 2007. Online.