The Medici themselves were bankers and latterly leaders of Florence's government. For the most part city states hired mercenaries through condotta (contracts) to do the fighting. Giovanni is really part of the Italian wars which it could be argued is a slightly later period than the true condottieri wars when the city states were at each other's throats. It's a fascinating period with lots of characters. Sforza, Malatesta, Colleoni, Carmagnola. There was a long period if relative peace after the 1440's only broken by the war in Ferrara that involved most of the main city-states eventually then in 1495 the Italian wars kick off.
