1. Several Italian city-states like Venice, Genoa, Milan, and Florence grew extremely wealthy through overseas trade in the 12th-15th centuries, fueling economic growth and patronage of the arts. 2. Many northern Italian cities established communes ruled by merchant oligarchies, though the common people sought more political power through popular uprisings. 3. By the 15th century, Italy was dominated by several powerful states including Venice, Milan, Florence, the Papal States, and Naples, who worked to maintain a balance of power to prevent any one from gaining complete control. However, the failure to unify made Italy vulnerable to foreign invasion and conquest.