Since several large city-states such as Milan and Venice growing rich on the prosperous Mediterranean trade routes, they had the money to commission grandiose cathedrals and works of art that still astound people today, but they also had the resources to hire armies and constantly fight to expand their power. Ironically, their very success was an impediment, as most prosperous city-states had far more money than available manpower because so many people worked in essential jobs in agriculture, crafts, or public works. Large bodies of men could not be spared for fighting, so if a city-state wanted to expand, it needed to hire an army to bolster the ranks.

Other factors limited the use of homegrown armies. City militias often got embroiled in the factional disputes that were rife in Italian urban politics, to the extent that the militia might take one side or another, or be so divided as to be ineffective against external enemies. The only way to avoid this was to bring in neutral, outside administrators all factions could agree on to handle local affairs in a supposedly impartial manner. Known as the podestà system, this odd method of running a government began to be common by the late 13th century, but this administration would need troops of its own and naturally hired outsiders, often non-Italians, to keep the peace.

Thus was born the condottieri (singular condottiero or condottiere). Meaning "contractor," it referred not only to the captains of mercenary bands but was also used as a general term for all the mercenaries in Italy during the Late Middle Ages and Renaissance. These flamboyant figures, sometimes of noble birth, had at their command experienced armies who hired themselves out to the highest bidder and kept to a strict code of professional ethics. Their fighting prowess and prestige soon put them in high demand, and rulers all across Italy eagerly bid for their services.