At the end of the war that had followed the 1420 agreement with the Duke of Milan (see the previous debate), Florence remained empty- handed and embittered by the territorial gains achieved by her ally, Venice. Now that the threat posed by the Duke seemed under control, however, the Florentines resumed their century-long design to take Lucca, the conduct of whose lord, during the last war, provided a pretext. The debate below is introduced by the words of Niccolò Machiavelli, who, in his Florentine Histories (IV, 18), offers an account of the events that is fully consistent with Guicciardini's:

Francesco Guicciardini (1483–1540) is primarily known for his writings on history and Florentine politics. From the sixteenth to the nineteenth century, his major work, The History of Italy, was translated six times into French, three times into English and Spanish, and once into Dutch and German, not to mention his Maxims and Reflections – a series of meditations grown out of his personal experiences – that had an even wider circulation. In a nutshell, it is no exaggeration to argue that Guicciardini's work deeply affected the European intellectual and political elites throughout the modern age.

Much of what Guicciardini says as a historian and a participant in the ongoing debate on Florentine political institutions inevitably deals with issues of international politics and foreign policy: The History of Italy is, in fact, the history of the relations between the Italian states and the European powers of the day, and the weight of the external world can be perceived in other important writings too. Yet, although we know quite a lot about Guicciardini the historian, his dark and pessimistic views on human affairs and his own brand of ‘republicanism’, precious little has been written about his perspective on international politics and foreign policy. As a modest way to begin to shed some light on this side of Guicciardini's thought, I have chosen to focus not so much on his entire production – which, if one includes the public and private correspondence, is monumental – but only on the part of it that seems immediately relevant to our purposes.

Guicciardini frequently engages in the analysis of political situations through pairs of opposing speeches, one in favour and one against any given policy on any given issue. Now, most of these pairs deal with foreign policy. As a whole, they constitute a remarkable collection of debates on war, peace, alliance and the like – in short, key issues in international affairs. Action takes place in various contexts: different Florentine institutions, the Venetian senate, the French royal council, the papal Curia, the imperial council. The structure of the debates is always straightforward: the first speaker argues that X is the right policy and Y the wrong one; the second speaker argues the opposite.

In the previous debate, which took place in 1507, the Venetian senate was called upon to choose between remaining loyal to the existing alliance with the King of France or accepting the Emperor's offers. In the debate below, which takes place in 1523, the issue looks the same, yet many things had changed in the mean time. To begin with, the King of France was now Francis I. Within a few months of his crowning, in 1515, Francis took the Duchy of Milan, from which his predecessor, Louis XII, had been expelled in 1513 at the hands of the Swiss. The Venetians, who had joined the French in yet another alliance, contributed to his success, and recovered part of what they had lost in 1509. In 1516, Charles of Habsburg became king of Spain, and three years later Holy Roman Emperor, thereby concentrating under his rule an enormous mass of dominions, stretching from the Netherlands to the Kingdom of Naples. Despite this vast territorial extension, many still considered France as the more formidable power of the two: her central position, wealth, population, military capabilities and centralised government were contrasted with the dispersion of Charles V's dominions, the economic backwardness of some of them (Spain), the large autonomies of others (the Netherlands and the Holy Roman Empire) and the Lutheran movement, all of which suggested that the Emperor could have but a precarious hold on all his territories, except for the lands of the House of Habsburg. The most evident bones of contention between Francis I and Charles V, in territorial terms, included Burgundy, Navarre, Naples and Milan.

In Italy, a papal–imperial alliance was made (May 1521) for the sake of driving the French out of Milan once more and restoring the Sforza dynasty. Guicciardini, incidentally, was dispatched as a commissioner to the papal army, and witnessed the military operations that led to the liberation of Milan (except for the citadel) in November and the almost complete withdrawal of the French from Lombardy the following spring. Although Francesco Sforza was now the ruler of Milan, it was clear that his position depended on the benevolence of Charles, who, at this point, was the master of most of Italy. His eyes were now set on Venice.

Although the French defeat at Pavia and the capture of King Francis I (24 February 1525) had placed Charles V in a position of uncontested superiority in Italy, the Emperor was not inclined to proceed now to a direct subjugation of the Italian states. His chronic lack of money made it imperative to find, first of all, the necessary financial resources to pay his troops; in addition, his desire to impose an unconditional surrender on France (see above, Chapter 8.) suggested that this was not the right time to risk an open conflict with the Italians. The latter, for their part, were holding their breath. According to Guicciardini,

Francesco Sforza was given the Duchy of Milan back – although his position was far from solid, for the imperial army was still in Lombardy and he had not received the formal investiture yet. Simultaneously, Charles opened negotiations with Pope Clement VII and the Venetians and accepted a number of minor Italian states under his protection.

From 1309 to 1377, the popes resided in Avignon, and many of their dominions in Central Italy fell into the hands of local lords. In 1353, Pope Innocent VI sent Gil Álvarez Carrillo de Albornoz, Cardinal of St Clement, into Italy, for the sake of restoring the papal temporal authority. The energetic policies of the Cardinal led to the rapid establishment of a strong and cohesive state that surrounded Florence on all sides and that included cities and territories to which the Florentine republic, in turn, aspired. The full restoration of papal jurisdiction over Perugia (1371), in particular, elicited palpable concern across all Tuscany. In addition, many in Florence feared that the faction connected to the Church (the Guelph party and the Albizzi family) might now be tempted to rely on the Pope's external support to rid itself of its political enemies. Finally, the arrogant style of government of the papal legates who were dispatched from Avignon to the dominions of the State of the Church soon alienated the various peoples who were subject to their rule and created additional tensions with their neighbours: above all, Florence. Despite all this, Florence joined a general anti-Milanese coalition with the Pope in 1372 (and renewed it in 1374), for the sake of checking the expansionist policies of Bernabò and Galeazzo Visconti, lords of Milan, in Northern Italy.

It is against this backdrop that, in the winter of 1374–5, the Legate of Bologna denied Florence permission to buy grain in Romagna, a region under his jurisdiction. In the following summer, a truce being signed with the Visconti (4 June 1375), he dismissed Sir John Hawkwood and his mercenary company, who immediately headed for Tuscany, looking for plunder and ransom. In Florence, many suspected that Hawkwood had passed into Tuscany upon the Legate's encouragement, for it was believed that the latter intended to take revenge on the Tuscan cities that had refused to contribute funding for his war against the Visconti, thus forcing him to suspend it. A plot designed to make Prato – a town under Florentine dominion – fall into Hawkwood's hands was foiled and Florence was forced to pay a huge sum of money to convince the English mercenary to evacuate her territory.

Despite the scepticism of the Venetian Senate (see the previous debate), the French did pass into Italy in 1523 – to no avail – and once more in the autumn of 1524. This time, Francis I himself was at the head of a powerful army. The Imperials did not have enough forces to defend Milan, devastated as it was by the plague; accordingly, they locked themselves up in several fortified places. Francis then began to lay siege to the most important of them: that is, Pavia. Despite the coalition that Charles V had managed to make in August 1523 with Henry VIII and all the most important Italian states, not to mention the alliance with the Venetians signed the month before, the Imperials received no assistance. In addition, their poor financial resources made their position even more precarious. Being concerned about their ability to sustain themselves further, upon the arrival of a contingent of Landsknechts the imperial generals decided to launch a surprise attack upon the French camp, in coordination with the troops under siege. In the early morning of 24 February 1525, Francis's army was annihilated in a two-hour battle that would change the course of history, and the King himself was wounded and captured, while a number of French noblemen who were fighting next to him were killed. Not only did this sensational result leave Italy at the mercy of Charles V, but also it pointed at a clear French inferiority vis-à-vis Spain on a European scale – an inferiority that the French kings will be able to attenuate, but not cancel, in decades of war to come.

The news of this astonishing victory reached Charles on 10 March. According to Guicciardini, his public reaction was extremely sober:

Nor did he show ‘either in his words or gestures, any sign of immoderate gladness, or of being puffed up in mind’. The debate below took place a few days later.