I. Piccolomini at the Council of Basel

When Piccolomini arrived at Basel in 1432 as secretary to Cardinal Domenico Capranica, the crusade against the Turks was bound up with the issue of union. It was above all in his letters that the young Sienese registered his views, and the first letter that related to crusade dates from 1436 when the council was debating the question of its own relocation in response to Greek antipathy toward travelling to Basel.Footnote ² In April, following a seven-month absence from the council on his Scottish mission, Piccolomini sent a long report to the civic government at Siena about the matter. He knew that the rulers of his native city would want to know about the relocation issue because Siena itself had hosted Martin V's council when plague compelled it to leave Pavia in 1423—Piccolomini himself, then in his late teens, had witnessed the council in session. In the course of an informed and alert commentary, Piccolomini points toward the odds favoring Mantua, but he concludes by declaring that Siena should not rule itself out because “many things can change.”Footnote ³

It is fascinating to see that in 1436 two aspects of crusade promotion which would preoccupy Piccolomini as pope more than two decades later were already at play: authority over the promotion of a crusade and the raising of enough money to make it viable. The question of authority shaped discussion both in the general sense of whether it was the council at Basel or Pope Eugenius IV who should take the lead in negotiating union with the Greeks, and in the narrower sense of whether Basel could issue indulgences to raise the money needed to make it possible for the Greeks to send their large delegation. Some people, Piccolomini writes, argued that, while the council had the authority, indulgences originating from Eugenius would be “stronger and more popular.” He explains further that the reason why the debate on indulgences has been so important is the “vast sums of money” required, not least because of the need to provide Constantinople with some military assistance, even at this early stage of the union talks. The union issue had always been meshed with the provision of armed help, though it was only later that a fully-fledged crusade would come into the picture. Raising money would become one of Pius II's biggest problems, so much so that on the eve of his great crusade, he was prepared to compromise the security of the papal state by selling its fortresses to raise cash.Footnote ⁴

Piccolomini did not let this topic lapse, undoubtedly because he knew that a council held at Siena would be very advantageous for his own career. In a letter written in August, he again considered Siena's prospects as the venue for the relocated council. He lobbied hard for Siena to make a realistic pitch. It could succeed if Siena was prepared to offer 25,000 ducats in advance, of which 10,000 would go to Constantinople for defense purposes while 15,000 would be used for travel costs. Repayment would come from indulgences and tenths levied by the council. The problem was the offer stemming from Medicean Florence, which reflected its superior resources and greater ambitions: 85,000 ducats, thirty houses to be placed at the council's disposal, four galleys, and a guarantee of food and rents at a fair price. Another big player, the Duke of Milan, was even prepared to place one of his towns—Pavia or Piacenza—entirely in the hands of the council.Footnote ⁵

At the end of October, Piccolomini wrote again, though one senses a growing awareness that the cause is a hopeless one. He admitted that the costs were challenging: the council's plan was that two galleys would set out in January 1437 carrying 300 crossbowmen, cash, and envoys, and entailing a total outlay of 70,000 ducats. In response, Piccolomini appealed to Siena's self-esteem: “Where will you find fame, if you let this chance go?” It was true that a question mark still hung over the council's authority to grant indulgences and raise a tenth, but Eugenius would back the idea if the council were to meet at Siena (because it would then be subject to papal control). Piccolomini set out a good deal more detail in his letter, all of it priced with considerable care. The 70,000 ducats would be a sound investment.Footnote ⁶ However, in another letter on the subject written in December 1436, Piccolomini stopped making the case for a Sienese council and simply reported on events, noting that Avignon, Savoy (in practice, Geneva), and Florence were now the top contenders, with Florence raising its bid to 120,000 ducats.Footnote ⁷

This valuable group of letters on union and its associated problems presents us with an ambitious and energetic young man, fully in command of detail, offering astute assessments of the political and financial aspects of one of the thorniest issues that faced the council of Basel in 1436. There is no indication of personal convictions or leanings, indeed Piccolomini is detached in his observation of how and why developments at Basel are taking place. The same can be said of his long letter of May 21, 1437 to his close friend Piero de Noceto. This letter holds an important place as Piccolomini's first account of the critical session of May 7, which showed that the council was split into two factions. The larger faction supported a move to Avignon, where the costs of union negotiations could be met by the taxation of the French church. The smaller faction—led by Cardinal Cesarini—opposed such a move, construing it as an unrealistic gesture of defiance against Eugenius IV.Footnote ⁸ The opening pages of Piccolomini's letter form one of the fullest accounts that we possess of the acute disagreements about relocation and its political ramifications, especially the intrigues of Eugenius IV and Charles VII of France—who was naturally keen to support Avignon's bid and willing to allow the taxation that underpinned it. With regard to the May 7 session, Piccolomini writes: “It was like watching two armies simultaneously preparing for battle, and once their lines were drawn up a fight was bound to occur.”Footnote ⁹ To anybody as familiar with the violence generated by factions in Italian cities as Piccolomini was, such bellicose language was worrying, and over the years this detached assessment of the effects of disagreement on the council's conduct would mutate—under the pressure of Piccolimini's need to justify his own change of allegiance—into the legenda negra of a council degenerating into uncontrollable chaos.Footnote ¹⁰ But even in the early summer of 1437, the situation at Basel had become so trying that in June Piccolomini wrote to Emperor Sigismund advising him that he might come to Basel to take charge, writing that this “will enable you both to restore peace in Christendom and to extend the boundaries of the empire.”Footnote ¹¹

The appeal to Sigismund was a desperate one—the emperor was busy consolidating his hold on the Czech lands and had lost patience with Basel—but it is revealing about Piccolomini's political outlook. He portrays the situation in the church as desperate: the council was divided and at its May 7 session had passed two irreconcilable decrees. At the same time, Piccolomini continues, the pope and council were at loggerheads, “so that he allows what the fathers forbid, and he absolves those whom they damn.” In such a dire situation, the need for an imperial initiative was clear, but in addition, Sigismund should give thought to the ramifications of the council's relocation. The pope and the Greeks favored Florence, and there was no more anti-imperial city than the historic capital of Guelfism. Meanwhile, Venice presented its own threat to the empire and rejoiced in a pope of Venetian origins. A Florentine council dominated by a Venetian pope would likely annul the decrees of Basel pushed through by German reforming zeal. The threat posed by this Veneto-Florentine-papal alliance must be met by a vigorous imperial response.Footnote ¹²

Although triggered by the relocation question, this letter is really about balances of power. One such balance concerned the whole of Christendom and involved papacy, empire, and council. The other was specifically Italian and had received a major shock from the return of the pope to Rome, the consequence of this being that the four great powers that existed in Piccolomini's childhood—Florence, Venice, Milan, and Naples—had become five. Against this background, the question of the council was bound to have ramifications for peninsular politics. Two things absent from the letter, or nearly so, are reform and the Turks. Piccolomini makes a brief reference to the loss of reform decrees—on elections and the retention of annates—which the Germans had promoted, but it is largely a tactical mention. It may seem curious that the Ottoman Turks are not brought into the picture, given the close connection between union and crusade, but Sigismund had recently spent time fighting them and Piccolomini sought to redirect the emperor's energies toward the empire's Italian lands. In fact, the 1437 letter is one of the earliest examples of a conundrum in Piccolomini's thinking which we will witness become more striking once he entered Habsburg service: where should imperial energies be directed, toward Italy or the Turks?

II. Piccolomini in the Service of Frederick III

Late in 1442, Piccolomini entered Habsburg service as a secretary, and a number of texts dating from the early months of the following year help us to see how his views evolved in accordance with his own changing circumstances and with the broader shifts in the political and ecclesiological landscape. In April 1443, he penned a long letter to Hartung von Kappel in which he set out his opinion on the relationship of pope and council.Footnote ¹³ Around the same time, he wrote one of his most engaging texts, the Pentalogus, which registers his early reactions to the venerable but complex and frustrating political organism within which he was now working.Footnote ¹⁴ Thirdly, there is an undated letter from Cardinal Giuliano Cesarini to Piccolomini in which the cardinal congratulates Piccolomini on his appointment and informs him that he hopes to be in Vienna to extend his congratulations in person. Cesarini explains that he will be there to arbitrate on the Hungarian succession, “so that he can apply himself the better and more readily to organizing the planned campaign against the Turks, the most ferocious enemies of the Catholic faith.”Footnote ¹⁵ In the wake of the council of Ferrara/Florence and the achievement of union, Cesarini was vigorously promoting a crusade on behalf of the papal court. It had become an important feature of international politics and remained so throughout the 1440s.

When one reads the letter to Hartung von Kappel, Piccolomini's views on the council in 1443 seem clear. When a council was sitting, Piccolomini believed that it held plenitudo potestatis and that the pope could do nothing without its assent.Footnote ¹⁶ In practice, however, Basel's authority had been steadily draining away since two landmark events in 1439: Eugenius's resounding success in bringing about church union at Florence in July, and the council's creation of an anti-pope in November. Piccolomini acted as master of ceremonies for Felix V's election and that distinction may have blunted his sensitivity to the disastrous impact the council's actions had on public opinion when they plunged the church into another schism. He must have realized that Basel's future would be shaped less by theological disputes about the nature of the church or the transmission of Peter's keys than by its ability to retain the support of the major powers. In this respect, Eugenius's energetic promotion of a crusade in the years that followed union could only be detrimental to Basel: it won him kudos, acted as camouflage for moves designed to undermine the council, and had the function of a shield against demands for reform—the argument being that saving Constantinople and assisting Hungary must take priority. After Florence, Basel could no longer mount an alternative program of supplying aid for the Greeks; its best hope lay in German skepticism about Rome's initiatives, together with Frederick III's espousal of the claim of his relative Ladislaus V, “the Posthumous,” to the Hungarian throne. This made the imperial court an opponent of Eugenius's crusade, whose practicalities were entrusted to the capable hands of Cardinal Cesarini. Eugenius favored the succession of Vladislaus I, in part because the pope shared the hopes of the Hungarian baronage that Vladislaus could bring Polish resources to bear against the Turks.

Both from the perspective of his ongoing allegiance to Basel and from that of his employer's political goals, Piccolomini therefore found himself not just distanced from the most significant anti-Turkish crusade to date in his lifetime, but hostile to it. The most instructive evidence for this is the letter which he wrote in the summer of 1443 to his friend Niccolò Amidano, in which he passed on news of Cesarini's activity. In it, Piccolomini accuses the two principal promoters of the crusade—Eugenius IV (whom Piccolomini calls by his given name, Gabriele) and Vladislaus I—of injustice: Eugenius for holding the papacy unjustly and Vladislaus I for holding the kingdom of Hungary unjustly. As for Cesarini, his abject failure in Bohemia in 1431 had already shown Piccolomini that he was not fortunate in war. The Venetians would not send the fleet needed for success, so the crusade would fail, and that would be a good thing too, Piccolomini argues. As the editors of an English translation of Piccolomini's letters recently commented, the letter “marks the emergence in Aeneas's correspondence of an issue that would dominate his later years, becoming the chief concern of his pontificate.”Footnote ¹⁷ This is quite right, but what merits emphasis is Piccolomini's rejection of crusade on this occasion due to the perverted intention of its promoters—he believes that both pope and king are acting sub colore passagii and that “God pays heed to the intention, not the activity.”Footnote ¹⁸ In another letter written at this point, Piccolomini comes close to saying that the Hungarians deserve to suffer at the hands of the Turks for not recognizing the rightful claim of Ladislaus V.Footnote ¹⁹ Setting vested interests aside, it followed that, for Piccolomini, a crusading response to the Ottomans only stood a chance of success if Christendom's divisions were first healed.

In this respect, the Pentalogus is a revealing text because Piccolomini takes a more measured view of the overall situation in the spring of 1443 than he was able to do in his letters. As its name implies, it is a conversation between five individuals: the author, the emperor, the new imperial chancellor Kaspar Schlick, Bishop of Freising Nicodemo della Scala, and Silvester Pflieger, the bishop of Chiemsee and later head of the Austrian chancery. Piccolomini offers ideas and opinions about a variety of issues relating to decision making, but what is particularly telling is his advice to Frederick on Basel and Italy. The context for this was a big initiative which Piccolomini, as secretary, must have known was in the offing, for in June 1443, the emperor would invite all the European powers to send envoys to a meeting (concilium) to follow the diet scheduled to take place at Nuremberg in the autumn, to work “for peace and the unity of the Church.”Footnote ²⁰ This would, in effect, be a third general council—neither Basel nor Florence—which Frederick had earlier suggested as the only exit from the impasse created by Felix V's election.Footnote ²¹ Given Habsburg ambitions in Hungary, the imperial initiative posed an implicit threat to Eugenius's crusade, and the pope must have feared that the only way he could buy Frederick's neutrality in the schism would be to make concessions on the Hungarian succession.

Piccolomini grasped the thorny question of whether an imperial intervention in the schism would be acceptable by the horns. His answer—as we would expect, given his 1437 appeal to Sigismund—was an emphatic yes, and it was backed up with substantial learning. But to be credible, such interventions must possess gravity, and on important matters like this, Frederick should use envoys rather than letters. Then came an intriguing suggestion. It was all very well, Frederick is made to complain, for Piccolomini to refer to the precedent of Constantine and the council of Nicaea; Constantine ruled the whole world and had endless resources at his disposal. Pflieger then suggests using the proceeds raised from indulgences by the council of Basel in order to pay the expenses of the Greek delegates. That money was still lying in chests in many places and it was perfectly legitimate to use it to end a different schism—a suggestion which had been made at the Mainz diet two years earlier.Footnote ²² In addition to which, Pflieger goes on to remark, the first item on the new council's agenda would be compensating Frederick for the cost of bringing it into being, as well as presiding over it. It would grant him a tenth or a twentieth on the clergy. Seven years after expounding to his native city the way in which a relocation of Basel could be funded with the help of indulgences and tenths, Piccolomini was revisiting the topic from the viewpoint of the straitened Habsburg court, and he used the same appeal to the prestige which would accrue, “to increase thereby the honour of the realm.”Footnote ²³

With the matter of a third general council settled, Piccolomini moves on to advocating an Italian expedition. The interest of his extended discussion resides in the fact that Piccolomini is facing a very hard sell, much as he would at the Regensburg and Frankfurt diets in 1454 and the Mantua congress in 1459 when he argued the case for a crusade. History was full of disastrous imperial expeditions to Italy in much the same way that it was full of disastrous crusades. Schlick is allowed to remind the group of the difficulties that Sigismund had encountered on his Romzug in 1432–1433, to which Piccolomini himself ruefully replies “quite so, Kaspar.”Footnote ²⁴ His humanistic training leads him to set up an opposition as strong as possible so that he can reveal his oratorical prowess in his counter-arguments. The counter-arguments in this instance, however, are notably less convincing than those which Piccolomini would later advance in respect to the crusade. He claims, for example, that the Italians are exhausted by war and will not be stirred by specious appeals to defend their liberty. On the contrary, they would welcome Frederick as a bringer of peace.Footnote ²⁵ It is hard not to detect here a similarity to the wishful thinking displayed by Piccolomini and other exponents of crusade about the readiness of subjugated Christian communities in the Balkans to rebel against the Turks once a crusade appeared.

The comparison with crusade advocacy becomes even more apparent when Piccolomini addresses the task of persuading the Germans to support an imperial expedition. The text's nature allows for some trenchant formulation of objections. Pflieger voices the downright opposition of those who look only to local advantage—“anybody who wants the kingdom can have it, I'll stay at home in my city”—and who roundly declare that if Frederick wants to go to Italy then he should pay.Footnote ²⁶ So how would the empire as a whole stand to gain from a real as opposed to a notional imperial presence in the peninsula? Piccolomini gives the difficult task of explaining the prospective gain to Frederick. Some of the gain would be material: German nobles would hold lordships and principalities in Italy, and German merchants would be able to trade directly rather than through the Venetians, Genoese, and Florentines.Footnote ²⁷ A second gain would be the enhancement of imperial prestige in Germany. When Frederick later argues the contrary case for devoting his energies to controlling Austria, Piccolomini urges him to think big: once Italy is under his control, so too will Germany be—“The outcome will be that Italy remains an obedient subject of the Empire because of the Germans, and Germany because of the Italians.”Footnote ²⁸ And thinking in narrowly dynastic terms, this would secure the imperial succession for the house of Austria, as well as the kingdoms of Bohemia and Hungary, for Ladislaus the Posthumous.Footnote ²⁹

The Pentalogus may thus be viewed as an early example of the style of persuasive argument which Piccolomini would deploy with admirable finesse a few years later in arenas where crusading was being discussed. As its editor observed, the praise accorded to German bellicosity—“Germany has always held the title of most warlike nation”—would be prominent in the great orations.Footnote ³⁰ It is not surprising that neither the Turks nor the crusade feature directly, due to the logjam created by the contested Hungarian succession. But topoi which had long been familiar in crusading rhetoric—above all the destructive effects of warfare between Christians, and the value of peace and unityFootnote ³¹ —make frequent appearances, and in his peroration, Piccolomini works his way toward a phraseology which would not be out of place in a crusade oration: “You would be bringing about the expansion of the Christian faith and the salvation of many peoples, a cause for which each good person should be ready not just to contribute money and assume burdens, but if the need arises to lay down his life.”Footnote ³² These last words may be explained by Piccolomini's assertion earlier in the argument that rebellion against the empire was a mortal sin and that anybody who perished fighting in a just war to suppress such a rebellion would be saved.Footnote ³³ Even so, the idea that an imperial expedition to Italy would involve the augmentum of the faith looks like an egregious exaggeration. To explain it, we need to return to the text's earlier topic, that of the schism and the third council suggestion, and their relation to the campaigns of Cesarini and Hunyadi in 1443 (the “long campaign” or longum bellum) and 1444 (the Varna disaster).

The proposal for a third council found little favor. It may well have stirred recollections of the disaster in 1409 when the attempt made by the council of Pisa to end the Great Schism by electing a new pope had the effect of creating a third papal obedience. But the 1443 project never got that far. The influential University of Bologna denied that Frederick possessed the authority to summon a council, referring to the achievement of union with the Greeks, and commenting that Frederick's unwelcome intervention could hinder the hoped-for follow-up union with the Armenians and the crusade which could ensue, “when Christ's faithful are summoned by Eugenius to arm themselves against the unbelievers.”Footnote ³⁴ Important rulers like Alfonso of Aragon and Charles VII of France ruled out the proposal, as did the pope himself. On August 25, 1443, Eugenius responded by calling his own meeting at Rome where envoys would discuss “the peace of Christendom, the reform of the Church, the well-being of the empire, the liberation of Europe from Turkish savagery, the recovery of the Holy Land and many other topics relating to your [namely Frederick's] office and glory.”Footnote ³⁵ It was a clever way to check Frederick's move, and at the end of the following month, Cardinal Carvajal took this Eugenian counter thrust a step further in a series of repudiations of the allegations that Basel had made against the pope. Contrary to Basel's claim that Eugenius had worked against Frederick's election, the pope had supported him, and in part because of his high hopes, for in his youth Frederick had visited Jerusalem as a pilgrim. If elected, he could therefore be expected to recover the sacred city from the enemies of the cross and help bring the eastern schismatics back into union with the church.Footnote ³⁶

The public responses by Rome, Vienna, and their agents—including Piccolomini—to the dramatic military events that unfolded between late 1443 and late 1444 were therefore clear cut. For the Habsburgs, the crusade was part fiction and part diversion, it concealed the unjust denial of Ladislaus the Posthumous's dynastic rights and it took minds off the urgent tasks of ending the schism and reforming the church. For the papal court, the crusade was the sequel to union and was crucial in order to save both Constantinople and Hungary. The opposition of schismatic and condemned Basel was to be expected, that of Frederick was contrary to his office and a sad disappointment. What is striking about the abundant correspondence of Piccolomini—writing both in a personal and in an official capacity—is that the disagreements remained courteous. Polemics were reserved for the two sides in the schism. Cesarini indeed remained a friend of Piccolomini—we have seen him congratulating Aeneas on his appointment—and in August 1443, Aeneas twice wrote him with the news from Italy, objectively relayed and tactfully omitting any reference to Hungary.Footnote ³⁷ In June 1444, Schlick even referred to an agreement whereby he would send Cesarini the latest news from Germany while the legate reciprocated with the Hungarian equivalent.Footnote ³⁸ When he wrote to a friendly cardinal in the summer of 1443, Piccolomini politely excused his lord from taking part in the forthcoming passagium against the Turks on the grounds of his commitments in the Czech lands. Frederick had, however, assured Cesarini and the envoys of Vladislaus I that he would do nothing to impede the passagium—though he would not stand idly by if the Poles took advantage of this to attack Ladislaus's supporters in Hungary.Footnote ³⁹ Not that the Habsburg court was any less prone to using leverage. Twice in the autumn of 1443, Piccolomini told Cardinal Louis d'Aleman, a leading protagonist at Basel, that it would be in the council's interest to grant the see of Freising to Kaspar Schlick's brother Heinrich, given the imminence of the Nuremberg diet and the planned third council that was attached to it.Footnote ⁴⁰

Piccolomini's official letters, which he wrote on behalf of Frederick and Schlick, nicely illustrate the tightrope walking act which Frederick's ambivalent position on the crusade imposed on his employees. From the start of the sequence, it is clear that he can express with unsurpassed eloquence and panache the lineaments of the imperial commitment to crusade and the associated discourse of peace and unity. Hungary is the “special shield of the Christian religion . . . and irreversible damage and danger could face almost all of Christianity from any further rending of that kingdom [by the war of succession].”Footnote ⁴¹ Writing to Cesarini in May 1443, Schlick comments that “there is no advantage in taking up arms against external foes, until peace at home is secured first.”Footnote ⁴² By the start of July, Schlick's letters were reflecting the sub colore passagii theme, with discretion in a letter to Cesarini—who had little option but to carry out his legatine duties—but with indignation to others.Footnote ⁴³ At the end of August, Schlick was still complaining to Cesarini about aggression toward his supporters, but he also commented in detail on military matters. Schlick had extensive military experience in central and eastern Europe, and his letter covered many issues, including the timing of the expedition—surely it was too late in the year to embark on a campaign now—the make-up of the Christian army, and the naval support required.Footnote ⁴⁴ A few weeks later, a similar letter was dispatched to the cardinal, with more advice—he should avoid taking cavalry through mountainous terrain. Piccolomini must have gained enormously from sharing this expertise. The court he served seems to have been genuinely torn between wanting to see the Turks defeated—“may the piety of God grant that this crusade (passagium) enjoys happy success!”—and fearing the boost that this would give to Vladislaus I's position.Footnote ⁴⁵

The success of the longum bellum of 1443 was bound to make this quandary worse. In letters to the pope and cardinals on May 1, 1444, Frederick lauded the great deeds of Ladislaus's forebears, including his father's campaigns “both against the Turks and against the Hussites,” and pleaded that Ladislaus should be given the chance to match them.Footnote ⁴⁶ But there was no denying the glory that Vladislaus had won by his daring campaign. In response, Vienna continued to promote the line that further achievement hinged on peace between Christians and the healing of the schism, hence the diet convened at Nuremberg in the spring of 1444.Footnote ⁴⁷ A particularly interesting exchange between Cesarini and Schlick occurred toward the end of May. Writing on May 21, Cesarini welcomed the prospect of the Nuremberg diet, but tried to steer its agenda in a direction which would complement rather than hinder what he was attempting to do in Hungary. He argued that Frederick should abandon his neutrality in the schism and embrace the cause of Eugenius IV. He should then throw himself into promoting “some sort of crusade [passagium] against the impious Saracens,” that is, to the Holy Land, using shipping which the pope and Venice would provide. Not only would this be appropriate to his office and the deeds of his imperial predecessors, it would be more fitting than the pursuit of “noxious and frivolous matters,” a hard-hitting but obscure phrase which could refer to intervention in the schism, Hungarian affairs, or both. Schlick's reply to this eccentric proposal was dated seven days later: the Hungarians could not expel the Turks from Europe by themselves—a much broader initiative was called for and Schlick suggested that Cesarini travel to see the princes and lobby in person. We have seen Piccolomini stressing the importance of such personal contact in the Pentalogus, but this was probably also an attempt to detach the cardinal from his unhealthy partnership with Vladislaus.Footnote ⁴⁸ There was no need, Schlick maintained, to separate crusading efforts into two strands: a strong, unified effort would both drive Sultan Murad from Europe and liberate Asia (Asiam quoque liberandam).Footnote ⁴⁹

The situation was transformed by the disaster at Varna on November 10, 1444 and the deaths there of Vladislaus and Cesarini. In the first place, nothing now stood in the way of the succession of Ladislaus V to the throne of Hungary. Though the question of the regency continued to trouble relations between Vienna and Buda, it could not be denied that the conduct of Hungary's defense by John Hunyadi was in the best interests of the kingdom and Christendom at large. Piccolomini was fascinated by Hunyadi, and his report on the second battle of Kosovo in 1448, the regent's worst defeat, is one of the key sources for the encounter despite his not having been anywhere near the field of battle.Footnote ⁵⁰ By that point, the second complicating factor in Piccolomini's early years of service to Frederick III, the schism, had also ceased to feature in his thinking about the Turks. He had remained aloof from the polemics for some years.Footnote ⁵¹ In 1445, he made his own peace with Eugenius IV, and this cleared the way for his ambition and ability to fashion a career trajectory that astonished contemporaries and has—understandably—led some historians since to question his sincerity: ordination in 1446, bishop of Trieste in 1447, and bishop of Siena in 1451.Footnote ⁵² At the same time, his rapprochement with Eugenius enabled him to play the key role in bringing about the acceptance of Eugenius's authority by the empire, sealed in 1448 in the concordat of Vienna. Piccolomini was now able to set out the position which remained his ideological stance through to his death: that both papacy and empire had roles to play to secure Christendom's well-being. Amongst other things, it was the message of his tract De ortu et auctoritate imperii of March 1446.Footnote ⁵³

When Pope Nicholas V crowned Frederick III at Rome in March 1452, Piccolomini gave two orations and one of them, Moyses vir Dei, was a call to crusade.Footnote ⁵⁴ The meeting of pope and emperor made crusade a natural topic, but so too did the dire situation facing the Greeks and eastern Christians following the disasters at Varna and Kosovo.Footnote ⁵⁵ There is no doubt that the Turks increasingly preoccupied Piccolomini in the nine years that separated their triumph at Varna from their capture of Constantinople. But his thinking about them still lacked the focus and urgency that the catastrophe of 1453 would bestow on it.Footnote ⁵⁶ This is apparent in the crusade oration of 1452, in which the conflation of Greece and the Holy Land, the Ottomans and the Mamluks, is as present as it had been a decade earlier, before Varna and Kosovo. Some of the rhetorical prowess of the post-1453 orations is on display, in particular Piccolomini's penchant for a tripartite structure based on just war ideas (in this instance commiseratio, utilitas rei, and honestas rei). But the treatment of the Turks remains lightweight: they will easily be defeated, and Frederick will not just save Greece and recover Jerusalem, but wipe out Islam.Footnote ⁵⁷ The difference between claims and reality is bizarre. In Piccolomini's defense, it should be pointed out that even Cesarini—his hero,Footnote ⁵⁸ as well as an immensely experienced man—had written in similar terms in May 1444. It seems that any discussion of an imperial passagium was deficient without a frame of reference that included the Holy Land. That said, the 1452 oration confirms the impression made by other sources that it was only the loss of Constantinople that crystallized in Piccolomini's mind a perception that the Ottoman Turks were the normative foe of a Christianitas whose ideological leadership he had come to vest jointly in papacy and empire. The tension between the authority of pope and general council had gone—the council of Basel had finally dissolved itself in 1449Footnote ⁵⁹ —but it had been replaced by another tension, this one even more debilitating: that between ideology and military capability. For just as the strength of the Ottomans became more apparent, the shortcomings of papacy and empire found in Piccolomini their most acute commentator.Footnote ⁶⁰

III. Cusa and the Crusade Before 1453

When Constantinople fell in 1453, one of the recipients of the letters Piccolomini wrote in response to the news was his friend Nicholas of Cusa, cardinal priest of S. Pietro in Vincoli. Piccolomini wrote first about other matters, but the bulk of the letter—nine pages in the printed edition—dealt with Constantinople. This section began with some short comments directly relating to its recipient. Thanks to Cusa's visit to the Byzantine capital sixteen years previously, Piccolomini wrote, the city was well-known to his friend: he was fully aware of its strategic significance, the size of its fortifications, the strength of the Turks, and the negligence of the Latins in allowing it to fall.Footnote ⁶¹ What followed was more general, indeed it constitutes a useful summary of Piccolomini's fully developed views on the Turks as uncivilized barbarians who must be resisted if the Christian faith was to survive. Piccolomini worked his way toward the urgent need for a common Christian response, which must be mobilized and led by emperor and pope. It was only at this point that he again personalized the commentary. He argued that Nicholas V must take care to dispatch good preachers, “amongst whom common opinion includes your good self.” Piccolomini believed victory over the Turks—indeed victory over the Saracens too—was certain if his advice was followed.Footnote ⁶²

It would be unwise to infer from this letter that its author hoped that Cusa would throw himself into promoting a crusade. Piccolomini was writing primarily to lobby on behalf of Frederick III regarding a popular cult of St. Lawrence that had sprung up at Stanz. The author did not indicate that he expected Cusa to be more shocked than others by the news from the east, notwithstanding his first-hand knowledge of Constantinople; and the reference to Cusa undertaking the preaching of a crusade could be simple flattery. But the fact remains that Piccolomini chose Cusa as the recipient of one of the letters in which he expounded at length his ideas about the Turks and the need for a crusading response. And this makes the letter a useful entry point to a discussion of Cusa's views, not least because his most well-known reaction to the fall of Constantinople was so singular and—at first sight—so different from that of the Sienese.

In 1433–1434, Cusa wrote his masterpiece, the De concordantia catholica, in an attempt to establish a balanced framework for authority within the church which would reconcile the claims of pope and council. Not long afterwards, the fathers at Basel engaged in debate both protracted and heated about whether their council possessed the authority to grant indulgences to pay for negotiations with the Greeks; we have observed Piccolomini lobbying for a Sienese bid to act as the location for the union talks. It does not appear that Cusa contributed toward the debate, but his text would have provided reasoned ammunition for those arguing for the indulgences. He asserted that “there is no doubt that the whole church has the power of the keys, to bind and loose, as long as it is united”;Footnote ⁶³ and he set out the case for plenitudo potestatis residing with all the apostles and hence with all bishops, who collectively were successors to St. Peter.Footnote ⁶⁴ In fact, the De concordantia argued the case for a moderate conciliarism not dissimilar to the one that Piccolomini would still be defending in 1443. Long before that date, however, Cusa had become a confirmed papalist—“the Hercules of the Eugenians” as Piccolomini called him in 1440.Footnote ⁶⁵ What triggered Cusa's move was the turbulent sessions of 1437, and his conviction that the assembly was dominated by men who showed insufficient respect for the papal office, which Cusa argued in De concordantia was a tenet of faith, “for that line or holy cathedra will endure without defect even to the consummation of the world.”Footnote ⁶⁶

Cusa fully concurred with Piccolomini that the emperor carried responsibility for the defense of the faith,Footnote ⁶⁷ and that his ability to discharge this role hinged on sound relations with the church.Footnote ⁶⁸ After 1437, this entailed persuading the emperor and princes to embrace the cause of the pope, and in the 1440s Cusa's activity on behalf of Eugenius included attendance at a series of imperial diets. At the 1442 Frankfurt diet, he delivered a vigorously pro-papal account of the way the union negotiations had been handled.Footnote ⁶⁹ At the 1444 Nuremberg diet, where the claims and accusations of the pope and council regarding union and crusade were debated as hotly as they had been at Basel itself in the 1430s, Cusa was vociferous in defense of Eugenius, and his response to the conciliar charge that the pope behaved simoniacally reflected his own work at Constantinople a few years earlier. Rather than collecting money by illicit means, he argued, the pope was spending it lavishly “for the health of the Church and expansion of the faith, as shown by his deeds in union with the eastern [Christians] and resistance to the Turks.”Footnote ⁷⁰ He emerges as an advocate of the Eugenian program of union and crusade, nor was he the only contemporary to see the union achieved at Florence as heralding a new age of Christian harmony, though Christian defeat at Varna and Kosovo soon applied a brake to such enthusiasm.

There are grounds for arguing that Eugenius's program was designed not just to gain ascendancy over Basel, but also to push active reform aspirations into the shadows.Footnote ⁷¹ Notwithstanding his own pluralism, this was not Cusa's goal, for after his promotion to cardinal in 1448, he was unstinting in his pursuit of reform.Footnote ⁷² This was manifested most clearly in his German legation of 1451–1452. The timing of the legation is crucial: it was linked to the 1450 Jubilee rather than to a call to crusade, as it almost certainly would have been after the fall of Constantinople. In a number of respects, though, Cusa's troubled and at best partially successful efforts at instituting grassroots reform in membris in the empire is both reminiscent of the series of legations created by Martin V in the 1420s to preach crusade and reform, and anticipated the legations devoted to crusade against Hussites and Turks in the post-1453 period.Footnote ⁷³ Cusa ruffled many feathers by his interventionism and aroused much suspicion by his liberal granting of indulgences in exchange for money. Years later, Gregor Heimburg would direct against him accusations similar to those made by Basel against Eugenius, charges which the diehard Austrian conciliarist Ebendorfer delighted in reporting at length.Footnote ⁷⁴ And through his insensitive treatment of local cults—like that of St. Lawrence which Piccolomini wrote to him about in 1453—Cusa left behind him a resentment of Rome which would mushroom in the second half of the century, finding in Pius II one of its most concerned commentators. The impression one receives from the Cusa legation is that this man who nurtured the twin goals of peace and unity lacked the personal skills to implement reform without damaging both.Footnote ⁷⁵

IV. The Response of Cusa and Piccolomini to the Loss of Constantinople, 1453–1464

The Ottoman capture of Constantinople in May 1453 was a watershed event in relations between the Christian and Islamic faiths, compelling both sides of the religious divide to consider the future. Piccolomini and Cusa responded with texts setting out ways in which bellicosity might be avoided. Piccolomini composed his response in 1461, three years after his election as pope. It took the form of a letter addressed to Mehmed II—though almost certainly never sent—inviting the victorious sultan to embrace the Christian faith. A drop of baptismal water, the pope wrote, would transform Mehmed from Christendom's most dangerous foe to its greatest ruler. The letter is a brilliant composition, at once elegant and incisive.Footnote ⁷⁶ But it remains enigmatic, and however one interprets it, there is no doubt that it cuts across the rest of the pope's writings and activity. Both in his capacity as Frederick's envoy at the Türkenreichstage of 1454–1455Footnote ⁷⁷ and in his papal reign (1458–1464), Piccolomini displayed a thoroughgoing commitment to the cause of a crusade against the Turks.Footnote ⁷⁸ Building on the solid foundations laid by Eugenius IV and Calixtus III, he established a robust link between crusade and papal authority. And while he continued to emphasize the importance of the imperial office, in practice he accepted the need to work toward pooled military contributions—under the stimulus of papal persuasion, encouragement, and initiative.

Cusa's reaction to the situation was more complex. His most substantial written response to the fall of Constantinople, the De pace fidei, was one of the most radical approaches toward the issue of religious violence ever penned. Its recent editors did not exaggerate when they wrote that the work is “nothing short of stunning in the boldness of its suggestion.”Footnote ⁷⁹ Writing with extraordinary speed in the late summer of 1453, Cusa argued that the best answer to the terrible savagery perpetrated during the Turkish capture of the city was to establish peace between the various faiths of mankind, and that this could be achieved by holding a colloquium attended by wise men speaking on behalf of not just different faiths like Christianity, Islam, and Judaism, but different regions practicing the same faith, such as Germany and Italy. The optimism pervading De pace fidei is admirably summed up in what is perhaps its most famous assertion, that “there is but one religion in a variety of practices” (non est nisi religio una in rituum varietate).Footnote ⁸⁰ It followed that the use of violence in the service of belief was based on misunderstanding. When reason was applied to the perceived differences, they either crumbled away or—like the stubborn refusal of the Jews to accept Christ's divinity—did not really matter because they posed no threat to peace.Footnote ⁸¹ The highest good, peace, could best be maintained by peaceful means.

De pace fidei is a profoundly original text, but I think it misguided to deduce from it that Cusa rejected crusade. It is true that a year after writing it, Cusa wrote to Juan de Segovia commending the Castilian's advocacy of missionary activity rather than warfare. He shared Segovia's conviction that the Christian faith could be successfully communicated to Muslims once misunderstandings had been cleared away; this approach would inform his Cribratio Alchorani of 1461, a sustained critique of the Qur'an. In it, Cusa argued that the church would do well to reflect on why God was allowing the Muslims to enjoy such military success; and history showed that the Christian faith actually thrived on persecution. Cusa's letter to Segovia is notably sympathetic in tone—Cusa was eager to establish contact again with a man whom he had known well when they had both been at Basel, and who had remained loyal to the conciliar cause.Footnote ⁸² But I shall argue that the best way to grasp Cusa's position on crusade after 1453 is to compare him with his former colleague, an approach which has been much facilitated by Anne Marie Wolf's pioneering study of Segovia's views on Islam.

Wolf has shown that Segovia rejected crusade, in fact he created what she termed “an anticrusading discourse.”Footnote ⁸³ He cited the failure of crusading in the east to argue that it was a singularly ineffective response to religious difference. He also claimed that the history of his native land showed that even when Muslims were conquered, they still resisted conversion. Most remarkably, he was impressed by the contrast between the abject failure of the entire sequence of Hussite crusades and the successful discussions with the utraquists which the council of Basel had pursued from 1431 onwards, in the teeth of opposition from Eugenius IV.Footnote ⁸⁴ The restoration of peace in central Europe after over a decade of devastating warfare had been the fruit of negotiation. Crusading did not bring peace; on the contrary, it was bound to generate in the Muslims a hatred for Christ, whose symbol the crusaders wore.Footnote ⁸⁵ Segovia was far from alone in celebrating the success of the protracted discussions with the utraquists and contrasting them with the military disasters that they followed.Footnote ⁸⁶ He was, however, highly unusual in arguing that the Hussite precedent could act as a model for discussions with the Muslims. Cesarini and Cusa had played major roles in the talks with the utraquists, but neither man seems to have advanced such an argument. In Segovia's case, the optimism appears to have been sprung from conversations that he had conducted with Muslims from Granada in 1431, which exerted a disproportionate impact on him. That he was naive about the Turks goes without saying: he believed that once the Muslims were convinced that Christians were not polytheists, they would stop attacking, a viewpoint which ignored the dynamic of Ottoman expansion.

Anne Marie Wolf has correctly stressed that Segovia's rejection of crusading placed him at odds with most of his contemporaries, and that he seems to have become marginalized in his last years, not least due to his isolation at a priory at Aiton, in the French Alps.Footnote ⁸⁷ Among the high-ranking ecclesiastics with whom he corresponded after the fall of Constantinople, the Burgundian Jean Germain expressed vigorous disagreement with Segovia's approach and an epistolary exchange with Piccolomini, which could have been very interesting, did not proceed beyond generalizations.Footnote ⁸⁸ We have seen that Cusa's response was warmly sympathetic, but it is important to note the early part of his letter to Segovia, which related the political and military aspects of the crusading program as it stood at the end of 1454. The diets convened that year at Regensburg and Frankfurt constituted the imperial response to the crisis in the east and scholars have recently come to recognize their full significance, not least due to their proceedings being published.Footnote ⁸⁹ Cusa explained to Segovia the part he had personally played at the Regensburg diet, which pope and emperor alike had required him to attend. At Regensburg, Cusa made an offer of naval assistance on Nicholas V's behalf, but once news reached him of the peace which Venice had made with the sultan, he realized that the planned naval operation was no longer practicable. Frederick III had asked Cusa to attend the Frankfurt diet where he was again to present Nicholas's naval offer, but the pope ordered him instead to negotiate peace terms between the Prussian estates and the Teutonic Knights.Footnote ⁹⁰

Using evidence from the proceedings at the Regensburg diet, Erich Meuthen has been able to fill out Cusa's own account of his role there. Given the substantial experience he had acquired on his German legation of 1451–1452, and his dual status as cardinal and imperial bishop, it was almost inevitable that pope and emperor alike would want Cusa to play a significant role, even if it was overshadowed in practice by Piccolomini's ebullient self-promotion. In Meuthen's words, “Cusa had a specific, political task to discharge at Regensburg.”Footnote ⁹¹ According to Piccolomini's own account, Cusa emphasized that the Greeks had brought disaster on their own heads by the pride and deceit they had shown during the negotiations about church union. Meuthen cautions against taking Piccolomini's account at face value,Footnote ⁹² but such Grecophobia was not only common at the time, but complemented Cusa's reflection, in his letter to Segovia, that the church would do well to consider why God was chastising it in this way. Nor did it stop Cusa from moving on to the practicalities of a military response: according to Piccolomini's account of the diet, “gravely and at length he addressed the location of the fallen city, the ways of its people, the power of the Turks and their military methods. And while he did not deny that the Greeks deserved all they had suffered, he nevertheless exhorted the Christians vehemently to avenge the injuries to their savior.”Footnote ⁹³

It followed that few were better placed than Cusa to pass on to Segovia detailed information about events. The upcoming diet of Wiener Neustadt, he wrote, would reconsider the crusade program, paying particular attention to the imperial contribution, offered in response to Hungarian lobbying at Frankfurt. Cusa told Segovia about the peace of Lodi, and the hope that Alfonso of Aragon might subscribe to it, in which case there was a chance of acquiring naval assistance from that quarter. If that did not transpire, then, Cusa wrote “I doubt that the Germans will help out, because it seems to them that this common cause (rem communem) affects the Italians most of all.” He narrated, too, the news from the Balkans, of a defeat inflicted on the Turks by the Serbs with Hungarian help, of military action in Albania, and of Turkish losses at sea. This section of the letter concludes with an insightful distinction between a crusade organized in the European interior and frontline resistance by communities that were both Catholic and Orthodox: “So while there exists no hope of a crusade (passagium), resistance (resistentia) has taken the form I have described.”Footnote ⁹⁴

While this reportage occupies only about a quarter of Cusa's letter to Segovia, it provides a useful balance to his speculative optimism later in the text, as well as the outright utopianism of De pace fidei. He was a man of action—not always a very successful one—as well as a highly original thinker.Footnote ⁹⁵ Invested with offices, he did his best to fulfil them. As Joachim Stieber put it in a fine analysis of Cusa's move from conciliarism to papalism, “While Cusanus has been honored [in] modern times primarily as a religious thinker and philosopher whose spiritual writings are seemingly above the church politics of the day, it is well to remember that his life was marked by political partisanship, as he labored, a veritable Christian Hercules, on behalf of the ecclesia militans.”Footnote ⁹⁶ Cusa the intellectual was attracted by the Segovian stance that crusade was unnecessary and counterproductive; and Cusa the diplomat was well aware that a passagium was probably a forlorn hope in any case. But duty called and isolation was pointless. At the end of his letter to Segovia, he begged his old friend to set aside his conciliarist convictions and come to Rome. There he could expound his ideas to Nicholas V in person; the pope's illness prevented him reading and he was very fond of Segovia. Cusa implored, “I am aware that you do not care much for the curia, but this matter is so important and so sacred, that we should do everything that we can on its behalf.” But as Wolf argues, it seems likely that Segovia's belief in the inherent value of discussion was bound up with his conciliarism.Footnote ⁹⁷ While there is no evidence that Segovia saw crusade as a papal instrument, his conciliarist convictions inevitably distanced him from both of his former Basel colleagues.Footnote ⁹⁸

We have seen that Cusa's response to the fall of Constantinople, as registered in his reported comments at Regensburg and the Segovia letter, was colored by his belief that disasters were inflicted by God to punish human sinfulness. It is therefore helpful that his reaction to the Christian victory at Belgrade in 1456 is extant in the form of a sermon which he gave on August 24, the same day that he received the news. In common with his contemporaries, Cusa clearly experienced enormous relief not just that the Turks could be defeated, but that God had listened to the prayers of the repentant faithful, saying: “The cause of resistance seemed hopeless. But when all seemed lost a few crusaders engaged the enemy of the cross, shouting to the Lord, whose faithful they professed themselves to be through the sign of the cross.”Footnote ⁹⁹ The signum crucis, which Segovia feared would alienate Muslims, was a wonderful morale booster for those who wore it. Some days later Cusa expressed high hopes for yet more success in the Balkans and beyond: the crusaders would subdue the eclectic Turkish army, made up of Tatars, Muslims, and Christian renegades, “and the lord of the crusaders, that is Christ crucified, will rule for all eternity,” bringing about the expansion of his faith “as far as the ends of the earth.”Footnote ¹⁰⁰

Such ecstatic dreams reflected those of the reigning pope, Calixtus III.Footnote ¹⁰¹ Cusa gives the impression of being in step with the thinking and policy of the curia, even if, as a German cardinal, he showed particular sensitivity to the concerns of his countrymen.Footnote ¹⁰² It should not be surprising that when Piccolomini became pope in 1458 and devoted his pontificate to the cause of crusade, he found in Cusa one of his most loyal supporters. His old colleague tried to maintain order at Rome—as legatus urbis in temporalibus—in 1459–1460 during his absence at the congress of Mantua, and Cusa was travelling northwards to join Pius at Ancona when he died, just three days before the pope, at Todi on August 11, 1464.Footnote ¹⁰³ The editors of the English translation of Pius's letters summed up the situation well: “The two old warriors, both of whom had begun as champions of unity at Basle, had, like their mentor Cardinal Cesarini, ended their lives away from Rome pursuing another ideal, a crusade in defense of Christendom.”Footnote ¹⁰⁴ On the face of it, papal authority over the crusade had emerged as the decisive victor in the three-cornered contest of papacy, empire, and council. The bull Execrabilis, which Pius issued at the close of the congress of Mantua, forbade appeals to a future general council, and in 1460 Frederick III had made it clear that he was uninterested in Pius's crusade program by giving the imperial princes free rein to subvert Cardinal Bessarion's attempt to implement the promises that they had made at Mantua.Footnote ¹⁰⁵ The way was thus clear for Pius's assertion of a papal crusading authority, which in the summer of 1464 he took as far as physical participation. In practice, however, that authority was severely circumscribed, and invoking conciliarist ideas became a key weapon in the hands of secular rulers who were opposed to papal policy—above all the French crown.Footnote ¹⁰⁶ The ghost of the cause on which both Piccolomini and Cusa had turned their backs many years earlier would haunt the papal office for decades to come.