However, by 1426, with Venice's inability to secure peace on its own terms evident, a majority of the local population had come to prefer a surrender to avoid the pillage that would accompany a forcible conquest.

In March, Venice formally declared war on the Ottomans, but even then the conservative mercantile aristocracy running the Republic were uninterested in raising an army sufficient to protect Thessalonica, let alone to force the Sultan to seek terms.

In exchange for his support, by the Treaty of Gallipoli the Byzantine emperor secured, among other concessions, the return of Thessalonica, part of its hinterland, the Chalcidice peninsula, and the coastal region between the rivers Strymon and Pineios.

In Thessalonica's case, a tendency to pursue increased independence from the imperial capital had been evident at least since the Zealot movement of the mid-14th century, and had been reinforced by Manuel II's autonomous regime in 1382–1387.

Just as during the 1383–1387 siege, this led to a sharp division of opinion within the city between factions supporting resistance, if necessary with Western European ("Latin") help, and those urging submission to the Ottomans.

[19][20] In June 1422, Burak Bey, the son of Evrenos, assisted by various Ottoman marcher-lords of the Balkans, besieged Thessalonica as well, and ravaged its suburbs and the western portion of Chalcidice.

[21][22] According to the city's metropolitan bishop, Symeon (in office 1416/17–1429), both he and Despot Andronikos sent repeated pleas for aid to Constantinople, but the imperial government was short of resources and preoccupied with its own problems.

[31][32] But the majority of the Great Council of Venice was still dominated by the more cautious tendencies of the merchant nobility that ruled the Republic and they feared the disruption to trade that open war with the Ottomans would bring.

[31] Since the Fourth Crusade, the Venetians had consciously adopted a policy of gradually acquiring outposts, fortresses and islands from the collapsing Byzantine Empire, providing bases that secured Venice's valuable trading links with the East.

The council sent notices to the Venetian colonies in the Aegean Sea (Negroponte, Nauplia, Tinos and Mykonos) and the vassal Duke of Naxos, to prepare ships to take possession of the city, while the Republic's bailo at Constantinople was instructed to secure the assent of Emperor Manuel.

[35][36] A week later Santo Venier and Niccolo Giorgio were named provveditori (plenipotentiary envoys) and tasked with going to Greece and, if Despot Andronikos were still willing, taking over the city and arranging for its defence by hiring mercenaries.

[40] This sentiment even included some members of the nobility: the contemporary Byzantine historian Doukas records that soon after taking over the city, the Venetians imprisoned four leading aristocrats, led by a certain Platyskalites, for their association with the Ottomans.

[41] The contemporary Venetian Morosini Codex records a story of a conspiracy – dismissed as "slanderous" by Donald Nicol[42] – led by Despot Andronikos to hand over the city to the Turks.

If he found the city under siege, Loredan was to attack Gallipoli (where he had scored a major victory in 1416[49]), hinder the passage of Ottoman troops over the Dardanelles, and if practicable, to try and stir up opposition to the Sultan among neighbouring rulers.

To emphasise the fact that Venice did not desire war, Loredan was instructed to inform the local Turkish commanders that his actions were only as a consequence of the imprisonment of Giorgio and the siege of Thessalonica, which they had acquired legally.

This dispute allowed the Ottomans to bring Serbia and Bosnia back into vassalage, and after Murad stopped Sigismund's advance at the Siege of Golubac in 1428, a truce was arranged between the two powers.

[52] In the meantime, despite the activities of Loredan around Gallipoli, the situation in Thessalonica was so dire by October 1424 that the Great Council had to authorise the dispatch to the city of between 150 and 200 soldiers, as well as supplies and money.

[53][55] Michiel was also instructed to make contact with the Sultan and pledge considerable sums to the Grand Vizier, Çandarlı Ibrahim Pasha, and other members of the Ottoman court, to gain a sympathetic hearing.

The first attempt to land, led by Alvise Loredan, was repulsed, and only after all the ships mustered their forces were the Venetians able to overcome Ottoman resistance in a four-hour-long battle: 41 Turks were killed, including Ismail Bey, and 30 taken prisoner.

He then captured the Platamon Castle, on the opposite side of the Thermaic Gulf, by storm, after setting fire to its main bailey when the Ottoman garrison refused to surrender.

Following Michiel's request, the Great Council sent 200 men from Padua to man Thessalonica and the forts of Kassandreia, and authorised the captain-general to maintain four galleys in the area.

[44][60][61] At the same time, according to the Codex Morosini, a pretender claiming to be Mustafa Çelebi[f] arrived in Thessalonica, and gathered a growing following of Turks who considered him to be the true son of Sultan Bayezid.

[65] On 4 June a new duke and captain were elected for Thessalonica, Paolo Contarini and Andrea Donato, after the first three pairs chosen all declined the post, despite the fine attached to refusal; a clear indication of the unwillingness of the Venetian nobles to undertake this unprofitable and perilous task.

[77][86] Rather than resulting in a military alliance, however, the prospect of a Venetian–Cypriot–Karamanid league served to bring the Ottomans closer with the other great Muslim power of the Eastern Mediterranean, the Mamluks of Egypt, and initiate a period where the two states made common cause against Latin presence in the area.

[79][88] The lack of food even jeopardised the city's defences, since many of the mercenary guards on the walls, paid by Venice with wheat instead of cash, defected to the Turks when their rations were late.

[89] The privations of the siege led to an exodus of the city's population, as citizens with the ability to leave sold their possessions and fled to Constantinople, other Venetian-controlled Greek territories, or to the Turks.

[94] In their embassy in July 1425, the Thessalonians submitted a list of 21 complaints and demands, including fixed rations of corn for the poor and the lowering of tax dues and suspension of arrears and debt-related punishments for the duration of the siege, since the closing of the gates meant that people could no longer access their fields, which were furthermore devastated by the Turks.

[78] As the historian Apostolos Vacalopoulos put it, the prevailing view quickly became that "since Thessalonica was bound sooner or later to fall into Turkish hands, it would be preferable to surrender peacefully there and then, and so avoid the sufferings which would ensue if the Turks had to take the city by force.

[127] In July, Hamza Bey signed a peace treaty with the Venetians (ratified on 4 September 1430) whereby Venice recognised its loss of Thessalonica, restored passage of the Dardanelles, and acknowledged Ottoman overlordship over Patras in the Morea, with an annual tribute of 236 ducats.

A few months after the fall of the city Ioannina surrendered to Hamza Bey and Carlo II Tocco accepted Ottoman suzerainty over the southern remnant of the Despotate of Epirus around Arta.