Before the Peace of Westphalia Italy was an organic part of a vast network of European interests. It was the centre of the Catholic Counter-Reformation and one of the main bases of Spanish imperialism. Spanish-Catholic political interests were connected with widespread economic interests in which the shipping, banks, industry and merchants of Genoa, Milan, Tuscany, Naples and Sicily played an important part. The Peace of Westphalia maimed Spanish imperialism and halted the Counter-Reformation. As an indirect result, Italy was relegated to the margins of European history and confined to a very minor place among the countries of Europe. Thus the Peace of Westphalia was also a date of fundamental importance in the history of Italy, although its effects came to be seen only with the passage of time. It did not at once terminate the conflicts in which the peninsula and its States were involved, the war between France and Spain and the War of Candia between Venice and the Turks; nor did it change the political map of Italy, the essential features of which were settled by the Peace of Cateau-Cambrésis (1559) and modified in some details by subsequent events, in particular by the Treaty of Cherasco (1631).

Spain remained mistress of her traditional domains, Milan, Naples, Sicily and Sardinia. By means of a series of strategic points she retained control of the Tyrrhenian Sea, which was vital to imperial communications, and of the States along its coast. The Genoese republic, with its own territories of Liguria and Corsica, continued to be a pawn of Spanish policy; it was watched over by the strategic strongholds of the Marquisate of Finale (on the Ligurian coast and under direct Spanish rule) and of the Lunigiana valley (between the Po valley and the Tyrrhenian, an area dotted with fiefs of the Malaspina family, who were theoretically vassals of the Empire, but in practice dependants of the Spanish governor at Milan).