No naval league materialized during the pontificate of Benedict XII, but his successor, Clement VI, oversaw the formation of two naval leagues, the first in 1343, which formed the preliminary wave of the Crusade of Smyrna, and the second in 1350. The first operation was officially proclaimed as a crusade by Clement VI in the summer of 1343, although negotiations between the Hospitallers, Cypriots and Venetians had been ongoing since 1341. In total it was decided that twenty galleys were to be fitted out for this league: six from Venice, six from the Hospitallers, four from the papacy, and four from Cyprus, a number slightly lower than the league of 1333-4 and with the absence of the French. The fleet was to gather at Negroponte on the Feast of All Saints (1 November) 1343.
Once the captains of the galleys were appointed and other logistical considerations taken care of, the fleet assembled in the Aegean in the winter of 1343-4. In the following spring naval operations were undertaken against the Turks, which initially achieved a similar level of success to those in 1333-4. In one encounter in May, the crusader galleys won a notable victory against the Turks at Longos, a harbour on Pallena (the western promontory of the Chalkidike peninsula), where they ambushed and burned a fleet of some sixty vessels and captured a close relative of a Turkish emir. In October this was followed by an even more impressive feat when the crusaders launched a surprise attack on Smyrna, where they managed to capture the harbour and harbour fortress of the city from Umur Pasha, but not the acropolis overlooking the city which remained in his hands. Thereafter, it is likely that some of the combatants on the galleys remained to garrison the fortress at Smyrna, but the league, presumably now somewhat depleted in strength, still managed to repel an assault from the Turks led by a high-ranking naval officer, Mustafa, who was captured.
These initial successes, however, proved to be short-lived, as on 17 January 1345 the crusade leaders, including the papal legate Henry of Asti, and the captains of the papal and Venetian galleys, Martino Zaccaria and Petro Zeno, were killed outside the walls of the city. The Venetians and the Hospitallers diverted reinforcements to Smyrna in the spring, but soon after the Aydin-oglus began launching new raids in the Aegean from their other ports, especially Ephesos. In the wake of this setback and the ensuing stalemate, Clement VI looked to the West for a suitable commander to lead a relief army to Smyrna and revive the fortunes of the failing crusade. The most enthusiastic and possibly only response to Clement’s call came from Humbert II, the young and wealthy Dauphin of Viennois. He took the cross and was officially named as captain-general of the Christian army in May 1345. After marching through northern Italy, where chronicles report many people taking the cross, Humbert, accompanied by an army of around one hundred knights and eight hundred footsoldiers, sailed from Venice for the Aegean, reaching Negroponte in December 1345, where he joined up with six galleys from the league; the four papal galleys and one each from the Hospitaller and Venetian contingents. When in the Aegean, Humbert made several unsuccessful attempts to recruit allies to bolster his force before he was attacked by a Genoese fleet commanded by Simone Vignoso who went on to capture the island of Chios, which Humbert had been considering as a potential base for the crusaders. After this setback, the dauphin sailed to Smyrna, arriving in July 1346. Despite Humbert’s arrival, however, after this point the unity of the league began to crumble as the Venetians sought peace with the Turks and the Hospitallers sided with the Genoese, even preventing Venetian ships from entering the port at Smyrna. This infighting, plus the outbreak of disease amongst the crusader camp, forced Humbert to withdraw to Rhodes, whence he soon after departed for western Europe. Fortunately for the crusaders, by 1347 the Hospitallers and the Venetians had managed to settle their differences and in the following spring the galleys of the league, combined with Hospitaller reinforcements, won a notable victory against the Turks of Aydin and Sarukhan off the island of Imbros. In the spring of 1348 the Latins were given another boost when Umur was killed at Smyrna, apparently shot by an arrow when assaulting the walls of the harbour fortress.
However, the progress of the crusaders was quickly put on hold by the arrival of the Black Death. The great pandemic had been contracted by the Genoese during the siege of Caffa by the Mongols of the Golden Horde in 1346, after which it was carried to Constantinople the following May and then to the western coast of Asia Minor and the European side of the Straits in autumn. By 1348 it had spread to most parts of Anatolia and the Aegean, where it reportedly killed more than in any other area. The disease also reached Italy and southern France, where it is estimated that up to half the population of Avignon died during a seven-month period. The Florentine chronicler Giovanni Villani, who is one of the most reliable informants on both western European and Aegean affairs, leaves a vivid testimony of the progress of the plague from the eastern Mediterranean:
Having grown in strength and vigour in Turkey and Greece and having spread thence over the whole Levant and Mesopotamia and Syria and Chaldea and Cyprus and Rhodes and all the islands of the Greek archipelago, the said pestilence leaped to Sicily, Sardinia and Corsica and Elba, and from there soon reached all the shores of the mainland [.] And many lands and cities were made desolate. And the plague lasted till -.
Here Villani deliberately left a blank space after the word `till’ to be filled in once the disease had been lifted from Florence – a task that was never fulfilled: Villani too fell victim to the Black Death before completing his work. Considering the virulence of this pandemic, it comes as no surprise to learn that crusading operations were severely hampered by this outbreak. To add to this, Romania was suffering a severe shortage of grain caused by the closure of the Black Sea markets. The crusaders were thus forced to seek a truce with Aydin, the negotiations for which dragged on for some years. By the time the leaders of the league met at Avignon in 1350 to discuss its future, the Turks had begun launching new raids into the Aegean, which led to the renewal of the league and not the agreement of a truce. This new league was officially confirmed in August 1350, when it was decided that a small flotilla of eight galleys was to be assembled in the Aegean; three each provided by Venice and the Hospitallers, and two more from Cyprus. However, only a few weeks later war broke out between Venice and Genoa, thus ending any hopes of a Venetian contribution to this league. Due to the Venetian-Genoese war, the lack of funds and the ravages of the Black Death, less than a year after it was re-formed, this second naval league was officially dissolved by Clement VI in the summer of 1351. A year later the pope, who had done so much to facilitate the formation of two naval leagues, died.