Campaign in Italy and Invasion of Sicily
Dreaming of an imperial crown, in 1301 Charles married the titular empress of Constantinople, Catherine of Courtenay. The marriage drew Charles closer to the papacy, as his new marriage needed the connivance of Pope Boniface VIII. Boniface saw Charles as a potential ally and tool to further papal influence; the pope desired to re-install a Catholic ruler on the throne of the Byzantine Empire and thus revive the Latin Empire, which Charles now had a claim to. Boniface was also eager to end the nearly 20-year long war between the papacy, Angevin Naples, and Sicily, and so hoped to have Charles' army invade Sicily.
Named papal vicar, Charles of Valois led a private French army into Italy. However, he soon lost himself in the complexity of Italian politics, namely the generational feud between the Guelphs and Ghibellines. Local nobles and church officials used his army as a tool against their political rivals, and men under his command massacred a crowd in Florence. When his army landed on the shores of Sicily in May 1302, it faced heavy resistance from the Sicilian population. Charles' army pushed inland, but became mired in attritional warfare in the hot Sicilian summer; after a disastrous attempt to besiege Sciacca, Charles' army found itself out of supplies and surrounded on the southern coast of Sicily. Rather than see his army destroyed, Charles negotiated the Peace of Caltabellotta with the Sicilian leadership, thus ending the war of the Vespers. The Sicilian campaign had been a disaster; Charles' battered army had been forced to evacuate the island without having fought a major battle, and the treaty ended Angevin and papal attempts to re-conquer Sicily.
After his marriage to Catherine, Charles decided to reclaim his wife's empire. To fulfil this eastern ambition he had to secure the support of all those influential political figures of the time. The first and foremost was his brother, Philip IV of France.
Indeed, Philip promised to help his brother and gave assurances that he would do so by offering him some money, but in reality, he was too enmeshed in the war with Flanders which was at a critical point as the French had suffered a major disaster at the battle of Courtrai in 1302 to seriously consider a crusader expedition to Byzantium, not least his conflict with pope Boniface VIII which erupted in 1302. Boniface VIII's publication of the bull Unam Sanctam in November 1302 which asserted the papal supremacy precipitated the crisis with the king of France. Following the publication of the bull Philip IV went on to publish a series of forged letters dated on 5 December to induce the national feeling of the French clergy and people. To be sure, the French king and his officials Guillame de Nogaret and Guillame de Plaisians condemned the pope in two assemblies that took place in March and June 1303 in Paris in front of the French the prelature and nobility. On his behalf Charles of Valois tried to mediate the situation between his brother and the pope but to no avail. The "outrage of Anagni" followed and the death of pope Boniface VIII thereon.
While in Sicily, where he negotiated the Peace of Caltabellotta, Charles of Valois confirmed and renewed an anti-Byzantine treaty with Charles II, king of Naples in Viterbo, on 11 March 1302. Charles then turned to the Robert II, Duke of Burgundy who, after having inherited from his father Hugh IV the rights to the kingdom of Thessalonica, conferred on the latter in 1266 by Baldwin II, the Latin emperor, had started showing interest on the matter by 1303. The son of Robert II, Hugh in the meantime swore allegiance to the titular empress Catherine of Courtenay, wife of Charles of Valois and on March 24, 1303 he became affianced to their daughter Catherine of Valois. Necessary precondition for this marriage alliance to take place was the young man to promise the recovery of his prospective wife inheritance and his future "kingdom". Some two years later in January 1305 the couple, Charles of Valois and Catherine of Courtenay confirmed Hugh V, Duke of Burgundy as in possession of the kingdom of Thessalonica. Insofar as Charles of Valois might really recover Constantinople the marriage of the issue of Valois-Courtenay and the confirmation of Hugh were of significance to the House of Burgundy because that would eventually make Hugh an emperor. That potential relationship to work, however, needed first the investment in material support with men and money from the House of Burgundy.
As any other crusader expedition such a plan needed papal endorsement and a plan for the conquest of Constantinople was no less a crusade since the Greeks were heretics and schismatics, thus the project was a very desirable enterprise and the pope was more favourable than not to such a possibility. On the other hand, the fall of Acre in 1291 to the Mamluks had reinvigorated crusader zeal in Western Europe and countless theoretic crusading projects were published and presented to successive popes for that matter from 1291 up to 1330. A profound discrepancy of objectives surfaces here which meant that the pope had to be convinces for such a crucial shift to take the stead of the primary enterprise, the recapture of Jerusalem. Thus, Charles of Valois requested the aid of the new pope, Benedict XI. His shortlived papacy did not amount to anything more than the grant of a tithe. The situation took a decisive turn in January 1305 with the election of Pope Clement V, who, as a French himself, was well disposed towards the royal house of France and eager to restore good relations with Philip IV and his family. With a rather positive climate of peace and cooperation with Philip IV, Clement V and Charles of Valois expedited things in approximately two years time and the crusade now seemed more than merely plausible. Suffice here to note that the stance of emperor Andronikos II Palaiologos who repudiated the Union of the churches that had been proclaimed at the Second Council of Lyons in 1274, offered the necessary justification to set in motion the papal propaganda machinery. That reason along with the faltered policies of the emperor in Asia Minor established the meaningful link that saw the recapture of Jerusalem as the afterthought of an elevated morale. Significantly, however, it had translated the wishful expedition of Charles of Valois to a crusade project which he eventually proclaimed.
The papal support aside, Charles of Valois had to win the maritime powers of Venice and Genoa since the insurmountable problem of his project was the logistics. Clement V mediated to Venice by writing to Doge Pietro Gradenigo, exhorting him to help Charles and tried to lure him into the latter's project by offering the privileges of the crusaders should they participate. By the same token he also wrote to Genoa advising them that the time had come for the Greeks to be brought back to the true faith. On his behalf Charles of Valois sent his emissaries to Genoa to appeal for assistance and to get a quote for the shipping costs of his prospective campaign and whether the commune was interested in allowing Charles to hire those ships. Genoa's interest by this time and on the face of its imperiled position in the East by the Catalan Company had been inseparable from those of the empire of Constantinople, so the decline of Charles' request in 1306 was the only possible stance. On the contrary, Venice, being hostile to the empire and Genoa alike, accepted Charles of Valois's proposals which culminated in a treaty on 19 December 1306. To further aid the cause, the pope on 3 June 1307 excommunicated Andronikos II and warned the rest of the Catholic powers that they too were facing excommunication should they help the emperor, not least forfeit their property to the church.
The European alliances notwithstanding, Charles of Valois tried to secure backing for his plans from various powers in the East, that is the Catalan Company which was a redoubtable army to be reckoned with as time and again it had proved. The Company's frivolous allegiance to Frederick III allowed for its opportunism as did the lack of competent leadership. Indeed, under their new leader at the time, Berengar de Rocafort, the Catalan Company became a vassal of Charles of Valois in summer of 1307. This development conditioned the attitude of the Serbs, who under their king Stephen Uroš II Milutin established connections with Charles of Valois that culminated in the treaty of Lys on 27 March 1308. Last in this broader scheme of allies to enter were the malcontents in the empire of Constantinople, genuine unionists, enemies of Andronikos II and men who feared more the Turks than they did the French. The documented negotiations with these Byzantine supporters lasted from summer 1307 to spring 1310 and some of their names are known: John and Constantine Monomachos, siblings of whom the former was the commander of the armed forces of Thessaloniki, a certain Constantine Limpidaris identifiable with the megas stratopedarches and protovestiarios Libadarios, and the monk Sophonias. Concurrently to these four, the archbishop of Andrianople Theoktistos was also of some import to the negotiations with Charles of Valois as he appears to have been in Paris for over five months for that matter. Understandably, the prime concern behind those figures' action was to find an able defender for the Asia Minor front against Turkish aggressiveness, and their best possible candidate at that particular time was apparently Charles of Valois. The conclusion of his eastern alliances came with the unionist fraction of the Armenian kingdom, that requested for Charles's help and made certain concessions to the Roman Catholic church by 1307.
Charles's expedition was to be launched between March 1307 and March 1308. However, after 1308 there was a diminution of diplomatic activity and gradual abandonment of his plans of conquest, which in part was owed to the candidature he was offered for the throne of the Holy Roman Empire after the German king's assassination in 1308. Besides, the death of wife Catherine of Courtenay in the same year played substantial role and along with a number of events that had occurred in the meantime weighted heavy towards the abort of the plan.
