The system of feudalism, bearing the same essential characteristics throughout Europe, had been a convienient way for lords to get military service from their vassals. Because the knight and his support (an esquire, a groom, a light cavalryman to scout) cost money and had to train from a young age, the lord gifted land to him so he might be economically secure. These men dominated the military scene of Europe until the advent of the longbow and Swiss pike. But in Italy, the feudal nobility had suffered a shattering in the Wars of the Investiture, and so things developed a little differently.
An Italian nobleman would not typically find himself with a large land or population base to draw military assets from. But Italy was atypical in the Middle Ages, because a lot of its wealth was based on trade - so they did have lots of money, just no vassals nor the land to tie them to. Due to the urban economy of Italy, what nobility there was had developed bourgeois habits slightly earlier than their North or West European counterparts would. In Italy, private war between the smallest city-states was still commonplace, and they needed soldiers. Enter the contractors, condottieri.
Freelance soldiering had been a commonplace during the Hundred Years War between France and England, when routiers - deserters - roamed the countryside, living off the land and the population. When the wars ended, a vast mass of these routiers surged south under the leadership of Englishman Sir John Hawkwood into Italy, where they joined a tradition already old. Knights left over from the Crusades and German chivalry seeking employment had already sold their service in Italy, the most audacious of which was the 'Great Company' that ran a huge protection racket. Hawkwood preferred to be addressed as either "Duke of Milan" or "Pope of Milan", being one of the first of the condottieri to become assimilated into the local aristocracy. The Sforza and Visconti families of Milan are a well-known case in point. The soldiers who had initially being welcomed because they seemed less likely to seek political ends than home-grown warrior bands had thus succumbed to this very temptation. Braccio de Montone, the first condottieri to establish his own state, fought a long and bitter war with Muzio Sforza, and the two men passed on the feud to their sons.
The condottieri in Italy fought primarily with lances on horseback. As with the armoured knights of old whom they look back upon romantically, they would also have servants acommpanying them on foot, armed with sword, cross-bow or arquebus. While the condottieri held sway over the Italian peninsula war became a highly tactical game - generals did not want to squander their assets and ruin their business, so they fought with care. Machiavelli viewed them with scorn for this and doubted their loyalty, saying the city states of Italy would be better off with civilian conscript armies, like those of Ancient Rome. In The Prince he told the story of Hiero the Syracusan who
made head of the army by the Syracusans, soon found out that a mercenary soldiery, constituted like our Italian condottieri was of no use; and it appearing to him that he could neither keep them nor let them go, he had them all cut to pieces, and afterwards made war with his own forces and not with aliens.
When in 1494 the Italian Wars began, and the Spanish tercios and French gen d'armes descended on the peninsula, the Italian forces could simply not match them. The French, supplemented by Swiss pikemen, made mincemeat of mounted troops. The Spanish did to the arquebus what the English had done to the longbow - turned it into a first-rate defensive weapon. The introduction of expensive artillery to the battlefield made the old Italian fortresses obsolete, and most of them simply parleyed straight away. During the sixteenth century the Italians regained the initiative in fortress design, making walls crooked so that fire could be concentrated from the defences on the attacking forces. They were surrounded with moats so the wall could not simply be breached willy-nilly. None of this happened quickly enough to save the Italians in the Italian Wars, however.
The Swiss for a time were the most reputed non-Italian condottieri because of the effectiveness of their phlanxes of pikemen. The Germans imitated them, and as warfare began to change with the introduction of firearms, the Germans also incorporated these and moved with the times - the Swiss, to whom mercenary soldiery had become a nationalised industry, failed to respond to the changing demands of warfare. Thus the German condottieri became the most highly sought-after. The condottieri remained the dominant force used for warfare in Europe, which explains the lack of major battles from the end of the Italian Wars to the Thirty Years' War. When nation states emerged which mobilised large amounts of their national resources into professional armies, the condottieri tradition died.