The siege of Thessalonica between 1422 and 1430 saw the Ottoman Empire, under Sultan Murad II, capture the city of Thessalonica. Afterwards, the city remained in Ottoman hands for the next five centuries until it became part of the Kingdom of Greece in 1912.
Thessalonica had already been under Ottoman control from 1387 to 1403 before returning to Byzantine rule in the aftermath of the Battle of Ankara. In 1422, after the Byzantines supported Mustafa Çelebi, a rival pretender against him, Murad attacked Thessalonica. Unable to provide manpower or resources for the city's defence, its ruler, Andronikos Palaiologos, handed it over to the Republic of Venice in September 1423. The Venetians attempted to persuade the Sultan to recognise their possession, but failed as Murad considered the city his by right and the Venetians to be interlopers. This impasse led to an Ottoman blockade of Thessalonica, which occasionally flared up with direct attacks on the city. At the same time, the conflict was mostly fought as a series of raids by both sides against the other's territories in the Balkans and the Aegean Islands. The Venetians repeatedly tried to apply pressure by blocking the passage of the Dardanelles at Gallipoli, with little success.
The blockade quickly reduced the inhabitants to near starvation, and led many to flee the city. The restrictions placed on them by the siege, the inability of Venice to properly supply and guard the city, the violations of their customary rights, and rampant profiteering by Venetian officials led to the formation of a pro-surrender party within the city, which gained strength among the inhabitants. The city's metropolitan bishop, Symeon, encouraged his flock to resist. 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. Venice's efforts to find allies against the Ottomans also failed: the other regional potentates either pursued their own course, were themselves antagonistic to the Venetians, or were defeated by the Ottomans.
After years of inconclusive exchanges, the two sides prepared for a final confrontation in 1429. 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 early 1430, Murad was able to concentrate his forces against Thessalonica, taking it by storm on 29 March 1430. The privations of the siege and the subsequent sack reduced the city to a shadow of its former self, from perhaps as many as 40,000 inhabitants to c. 2,000, and necessitated large-scale resettlement in the following years. Venice concluded a peace treaty with the Sultan in July, recognising the new status quo. Over the next few decades, the antagonism between Venice and the Ottomans morphed into a rivalry over control of Albania.
Background
In the 14th century, the nascent Ottoman Beylik was a rising power in the Near East. After subduing much of Anatolia, with the fall of Gallipoli in 1354, the Ottoman Turks also acquired a foothold in the Balkans. The Christian powers of the region, notably the declining Byzantine Empire, were weak and divided, allowing a rapid Turkish expansion across the region, conducted both by the Ottomans themselves and by semi-independent Turkish ghazi warrior-bands. In 1369 the Ottoman Turks were able to capture Adrianople, the third-most important city of the Byzantine Empire after its capital Constantinople and Thessalonica. Thessalonica, ruled by the Byzantine prince and future emperor Manuel II Palaiologos (r. 1391–1425), itself surrendered in 1387 after a lengthy siege (1383–1387), along with the cities of Christopolis and Chrysopolis.
Initially the surrendered cities were allowed complete autonomy in exchange for payment of the haraç poll tax. Following the death of Emperor John V Palaiologos in 1391, however, Manuel II escaped Ottoman custody and went to Constantinople, where he was crowned emperor, succeeding his father. This angered Sultan Bayezid I, who laid waste to the remaining Byzantine territories, and then turned on Chrysopolis, which was captured by storm and largely destroyed. Thessalonica submitted again to Ottoman rule at this time, possibly after a brief period of resistance, but was treated more leniently: although the city was brought under full Ottoman control, the Christian population and the Church retained most of their possessions, and the city retained its institutions.
Thessalonica remained in Ottoman hands until 1403, when Emperor Manuel II sided with Bayezid's eldest son Süleyman in the Ottoman succession struggle that broke out following the crushing defeat of the Ottomans and the capture of Bayezid at the Battle of Ankara against the Turco-Mongol conqueror Timur in 1402. 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.
Despite the restoration of Byzantine rule, relations between Thessalonica and Constantinople remained troubled, with Thessalonica's local aristocracy jealously guarding their extensive privileges, which according to modern scholars amounted to virtual autonomy. This was part of a wider phenomenon attested for several cities during the last century of Byzantine history, as central authority weakened and centrifugal tendencies manifested themselves. 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. Thus, after they returned to Byzantine control, Thessalonica and the surrounding region were given as an autonomous appanage to Manuel II's nephew, John VII Palaiologos. After his death in 1408, he was succeeded by Manuel's third son, the Despot, Andronikos Palaiologos, who was supervised by Demetrios Leontares until 1415. During this time, Thessalonica enjoyed a period of relative peace and prosperity, as the Turks were preoccupied with their own civil war, although it was attacked by the rival Ottoman pretenders in 1412 (by Musa Çelebi) and 1416 (during the uprising of Mustafa Çelebi against Mehmed I). Once the Ottoman civil war ended, the Turkish pressure on the city built up again. 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.
First Ottoman attacks and transfer of the city to Venice
The eventual victor in the Ottoman civil war, Mehmed I (r. 1413–1421), maintained good relations with the Byzantines who had supported him. The accession of Murad II (r. 1422–1451) changed the situation, as John VIII Palaiologos (r. 1425–1448), the heir-apparent and de facto regent for the ailing Manuel II, set up Mustafa Çelebi as a rival to Murad. After defeating his opponent, Murad, determined to extinguish the remnants of the Byzantine state, laid siege, unsuccessfully, to Constantinople from 10 June to 6 September 1422. 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.
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. Eventually, a single unnamed commander was sent to the city, but he brought neither men nor money with him. This commander proposed setting up a common fund of the citizens to support the defence, but this proposal met with vehement opposition, particularly from the wealthy aristocrats, who would naturally have borne the brunt of the cost. The common people likewise proved unwilling to contribute; when the news spread that the Ottomans had offered a peaceful settlement, provided that Despot Andronikos left the city, the commoners even rioted in favour of an accommodation with the Ottomans.
At that point a group of aristocrats persuaded the Despot to seek the assistance of the Republic of Venice, an initiative probably taken without consulting Constantinople. In spring 1423, via the Venetian colony of Negroponte, he informed the Venetians of his intention to hand over the city to them. When he informed the Venetians, they were appalled. The only conditions Andronikos attached to his offer were that the property, customs and privileges of the city's inhabitants, their right to trade and come and go freely, and the position of the city's Orthodox Church be respected, and that Venice pledge to defend the city against the Ottomans. The 16th-century chronicler Pseudo-Sphrantzes claims that Andronikos sold the city for 50,000 ducats, and this statement was often accepted by scholars until the mid-20th century. This is not mentioned in any other source, nor is it found in the original documents pertaining to the affair, as shown by the scholars Konstantinos Mertzios and Paul Lemerle. On the other hand, the Venetian envoys appointed to oversee the handover were authorised to provide a sum of 20,000–40,000 aspers from the revenue of the city as a yearly subsidy to Andronikos, should he request it.
The offer arrived in Venice at an opportune time. The election of Francesco Foscari on 15 April 1423 as Doge of Venice had placed a proponent of a more aggressive and unyielding stance against Ottoman expansionism at the head of the Republic. 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. 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. For some time Venice had viewed Thessalonica as a possible expansion target, especially as Constantinople seemed to be on the verge of falling to the Turks. Thus in 1419, Venice re-established a consulate in the city, headed by a local Greek, George Philomati, and after his death in 1422 by his brother Demetrios.
At a session of the Great Council on 7 July 1423, Andronikos' offer was accepted. 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. 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. Giorgio was then to go before the Sultan, inform him of Venice's acquisition of the city and justify it as an expedient to prevent the city from being captured by other Christians, who might be hostile to the Sultan. The envoys were also to arrange for peace both between the Sultan and the Republic, and between the Sultan and Emperor Manuel. Emperor Manuel evidently gave his assent to the proposal, for on 14 September 1423 six Venetian galleys, accompanied by one Byzantine galley, entered the harbour of Thessalonica. The Venetians were greeted by a jubilant population as saviours. For the Thessalonians Venetian rule meant not only security from the Turks (some 5,000 Ottoman troops were blockading the landward city walls) but, more immediately, a secure flow of supplies.
Nevertheless, large segments of the population continued to support the seeking of a settlement with the Ottomans; the writings of Metropolitan Symeon record that a number of inhabitants fled at this time to the Ottomans. 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. The four men were exiled, first to Crete, and then to Venice itself and finally to Padua. Only after the fall of Thessalonica in 1430 were the two survivors released. The contemporary Venetian Morosini Codex records a story of a conspiracy – dismissed as "slanderous" by Donald Nicol – led by Despot Andronikos to hand over the city to the Turks. The plot was reportedly discovered in November 1423, and Andronikos and his supporters were exiled, with the Despot sent to Nauplia.
Diplomatic and military events
Initial Venetian and Ottoman approaches
The Venetians hoped to secure Ottoman consent to the occupation of Thessalonica. However, when the provveditore Giorgio attempted to carry out his mission to the Sultan's court, probably in February 1424, he was unsuccessful to the point of being arrested and imprisoned by Murad. The Ottomans refused to accept the handover, considering the Venetian presence illegal on account of their previous right to the city through conquest. The Ottoman attitude was summed up by the reply allegedly given by Murad to Venetian ambassadors seeking peace, as recorded by Doukas:
This city is my paternal property. My grandfather Bayazid, by the might of his hand, wrested her from the Romans [the Byzantines]. Had the Romans prevailed over me, they would have cause to exclaim, 'He is unjust!' But you are Latins from Italy, why have you trespassed into these parts? You have the choice of withdrawing. If you do not, I will come posthaste.