Help understanding the expansion of Italian City-States during the early renaissance.

Money basically. It does not have a direct relation to the warfare aspect but you can compare it to the rise of the middle class in modern times.

The renaissance was a re-birth of art and science in Italy, so because people had new discoveries, inventions and ideas coming at them from every side, they had the spark of civilization ignited and while the feudal were easing there imperialistic/papal hold, the poor were eagerly meeting them half way in demanding better standards of living. And you have to consider the fact that with merchants, it not just businessmen that come up. These nouveau riche will demand a whole host of services like accountants and bankers, doctors and lawyers and teachers; and a whole cycle is put into motion that has become the predominant force of social transformation.

There was open warfare, the French had wrested quite some area from the Rome-based papacy but they soon lost it due to negligence of local issues and not being close to the newly won over people. It should be noted that, foreigners were invited into Italy by local dukes and princes to avoid the take over of their fiefdoms by other Italian rivals.

Don’t you just hate AP___ History?~ I would say expansion of culture.

Because these factions are pointing out weaknesses without solving them, the merchants can take advantage of them and the weaknesses will not be fixed. To further this, the opposition will do anything to maintain that weakness, making it easier for the merchants to conduct business.

Example: The papacy points out the ridiculously high taxes to a merchant. Then, the government would point out to the lord some Catholic law that prevents the worker from maximizing his profits. Both factions want to appease the merchant, so they lower the taxes and repeal the law. The businessman thrives.

Any time you have two conflicting parties, they dedicate their resources to that conflict. But you still have to have goods and services for your citizenry, and you still need to be able to have a market for goods that your citizenry produces. There is always a third party group that becomes the business agent for everyone. Like Switzerland in WWII. Like @Mtl_zack alluded to, in times of conflict there is money to be made in neutrality of the business agent.

So in a way, it’s war profiteering?

Yes, but in a more subtle way, because the merchant class acquires power as well as wealth.

Look at the Civil War. The south had cotton, the north had mills, both needed cash to finance the war. South sells cotton to england, england sells cotton to the north.

Business is about opportunity.