Byzantine civil war of 1341 – 47 The Byzantine civil war of 1341 – 1347 , sometimes referred to as the Second Palaiologan Civil War , was a conflict that broke out after the death of Andronikos III Palaiologos over the guardianship of his nine - year - old son and heir , John V Palaiologos . It pitted on the one hand Andronikos III ' s chief minister , John VI Kantakouzenos , and on the other the Empress - Dowager Anna of Savoy , the Patriarch of Constantinople John XIV Kalekas , and the " megas doux " Alexios Apokaukos . The war polarized Byzantine society along class lines , with the aristocracy backing Kantakouzenos and the lower and middle classes supporting the regency . To a lesser extent , the conflict acquired religious overtones . Byzantium was embroiled in the Hesychast controversy , and adherence to the mystical doctrine of Hesychasm was often equated with support for Kantakouzenos . As the chief aide and closest friend of Emperor Andronikos III , Kantakouzenos became regent for the under - age John V upon the Emperor ' s death in June 1341 . While Kantakouzenos was absent from Constantinople in September the same year , a " coup d ' état " led by Alexios Apokaukos and the Patriarch John XIV secured the support of Empress Anna and established a new regency . In response , Kantakouzenos ' army and supporters proclaimed him co - emperor in October , cementing the rift between himself and the new regency . The split immediately escalated into armed conflict . During the first years of the war , forces of the new regency prevailed . In the wake of several anti - aristocratic uprisings , most notably that of the Zealots in Thessalonica , a majority of the cities in Thrace and Macedonia came under regency control . With assistance from Stephen Dushan of Serbia and Umur Beg of Aydin , Kantakouzenos successfully reversed these gains . By 1345 , despite Dushan ' s defection to the opposition and the withdrawal of Umur , Kantakouzenos retained the upper hand through the assistance of Orhan , ruler of the Ottoman emirate . The June 1345 murder of " megas doux " Apokaukos , the regency ' s chief administrator , dealt the regency a severe blow . Formally crowned as emperor in Adrianople in 1346 , Kantakouzenos entered Constantinople on 3 February 1347 . By agreement , he was to rule for ten years as the senior emperor and regent for John V , until the boy came of age and ruled alongside him . Despite this apparent victory , subsequent resumption of the civil war forced John VI Kantakouzenos to abdicate and retire to become a monk in 1354 . The consequences of the prolonged conflict proved disastrous for the Empire , which had regained a measure of stability under Andronikos III . Seven years of warfare , the presence of marauding armies , social turmoil , and the advent of the Black Death devastated Byzantium and reduced it to a rump state . The conflict also allowed Dushan to conquer Albania , Epirus and most of Macedonia , where he established the Serbian Empire . The Bulgarian Empire also acquired territory north of the Evros river . Background : Byzantium in the early 14th century . In 1341 , the once - mighty Byzantine Empire was in a state of flux . Despite the restoration of the Empire ' s capital to Constantinople and the recovery of a measure of its former power by Michael VIII Palaiologos ( r . 1259 – 1282 ) , the policies implemented during his reign had exhausted the state ' s resources , and the Empire ' s strength waned under his successor , Andronikos II Palaiologos ( r . 1282 – 1328 ) . During Andronikos II ' s long reign , the remaining Byzantine possessions in Asia Minor slowly fell to the advancing Turks , most notably the newly established Ottoman emirate . This caused a flood of refugees into Byzantium ' s European provinces , while at the same time the Catalan Company wrought havoc in the imperial domains . Taxes also rose dramatically to finance tributes to the Empire ' s enemies . A combination of these failures and personal ambition moved the Emperor ' s grandson and heir , the young Andronikos III Palaiologos , to revolt . Supported by a group of young aristocrats led by John Kantakouzenos and Syrgiannes Palaiologos , Andronikos III deposed his grandfather after a series of conflicts during the 1320s . Although successful in removing the old Emperor from power , the war did not augur well for the future , as the Empire ' s neighbours — the Serbs , Bulgarians , Turks , Genoese and Venetians — took advantage of Byzantine infighting to gain territory or expand their influence within the Empire . The only son of a former governor of the Byzantine holdings in the Morea , John Kantakouzenos was related to the Palaiologoi through his mother . He inherited vast estates in Macedonia , Thrace and Thessaly , and became a childhood friend and the closest and most trusted advisor of Andronikos III . During Andronikos III ' s reign ( 1328 – 1341 ) , John Kantakouzenos acted as his chief minister , holding the office of " megas domestikos " , commander - in - chief of the Byzantine army . The relationship between the two remained close , and in 1330 , when the heirless Andronikos III ( John V was born in 1332 ) fell ill he insisted that Kantakouzenos be proclaimed Emperor or regent after his death . Their ties were further strengthened in the spring of 1341 , when the latter ' s eldest son , Matthew Kantakouzenos , wed Irene Palaiologina , a cousin of the Emperor . Unlike Andronikos II , who had disbanded the Byzantine army and navy , and who favoured monks and intellectuals , Andronikos III was an energetic ruler who personally led his forces in military campaigns . In 1329 , his first campaign against the Ottomans resulted in a disastrous defeat at the Battle of Pelekanos , after which the Byzantine position in Bithynia rapidly collapsed . Subsequent sorties into the Balkans were nevertheless successful in shoring up Andronikos ' tottering realm . Thessaly and the Despotate of Epirus , two territories separated from the Empire after the Fourth Crusade , were restored to imperial rule , almost without bloodshed in 1328 and 1337 respectively . Andronikos III also rebuilt a modest fleet , which allowed him to recover the rich and strategically placed island of Chios from the Genoese Zaccaria family in 1329 as well as to claim the allegiance of Andreolo Cattaneo , the Genoese governor of Phocaea on the Anatolian mainland . In 1335 , however , Cattaneo with Genoese assistance captured the island of Lesbos . The Emperor led a fleet to recover it and Phocaea , and requested the aid of the Turkish emirs of Saruhan and Aydin . Saruhan sent troops and supplies , but Aydin ' s ruler Umur Beg came to meet the Emperor in person . It was during this encounter that Kantakouzenos and Umur established a long - lasting close friendship and alliance . A war with Serbia in 1331 – 1334 proved less successful for the Emperor when several towns in Macedonia were captured by the Serbs , led by the renegade Syrgiannes Palaiologos . These gains were only curtailed when the assassination of Syrgiannes and the threat of a Hungarian invasion forced the Serbian ruler , Stephen Dushan , to seek a negotiated settlement . The subsequent peace treaty concluded between Andronikos III and Dushan was important for the future of Byzantine - Serbian relations . For the first time , the Byzantines recognized the extensive gains the Serbs had made at the Empire ' s expense in the central Balkans during Andronikos II ' s reign . In the aftermath of the pact , Dushan also moved his seat , and with it his realm ' s centre of gravity , south to Prilep . Although the loss of Asia Minor proved irreversible , successes in Epirus and Thessaly led to a consolidation of the Empire in the Greek - speaking lands of the southern Balkans . Andronikos III and Kantakouzenos planned further campaigns to recover the Latin principalities of southern Greece , a project of major long - term importance , for , as the historian Donald Nicol writes , " if the whole peninsula of Greece could be united under Byzantine government then the Empire would once again be a homogeneous structure , able to stand up to the Serbians , the Italians and its other enemies . It would be small , but it would be a compact and manageable economic and administrative unit running from Cape Matapan to Thessalonica and Constantinople " . Kantakouzenos ' regency : June – September 1341 . Following a short illness , on the night of 14 – 15 June 1341 the emperor Andronikos III died at the relatively early age of 45 . His nine - year - old son John ( John V ) was the obvious successor , but he had not been officially proclaimed or crowned as co - emperor . This left a legal vacuum , and raised the question of who would lead the Empire ' s government . According to Byzantine custom , the empress - dowager automatically headed any regency . Nevertheless , despite the lack of any formal appointment , Kantakouzenos placed Andronikos III ' s sons and the Empress - dowager Anna of Savoy under armed guard in the palace , and in a meeting of the Byzantine Senate claimed for himself the regency and governance of the state by virtue of his close association with the deceased Emperor . He also demanded that John V marry forthwith his own daughter Helena Kantakouzene . This claim was disputed by Patriarch John XIV Kalekas , who presented a document from Andronikos dating from 1334 , assigning to him the care of the imperial family in the case of his death . Only after a demonstration of the capital ' s troops on 20 June did Kantakouzenos secure recognition as regent and control of the reins of government , as well as maintaining control over the army as its " megas domestikos " . Nevertheless , opposition to Kantakouzenos began to coalesce around three figures : the Patriarch , a forceful man determined to have a voice in the governance of the Empire , the Empress - regent , who feared that Kantakouzenos would dispossess her son , and last but not least Alexios Apokaukos , the ambitious " megas doux " ( commander - in - chief of the navy ) and head of the bureaucracy . A " new man " promoted to high office as the protégé of Andronikos III and possibly the richest man in the Empire by 1341 , Apokaukos was distrusted by the hereditary aristocracy . The only surviving narrative accounts of the period , Kantakouzenos ' s memoirs and the history of Nikephoros Gregoras , with their pro - aristocracy bias , paint a very negative picture of the man . According to Kantakouzenos , Apokaukos ' adherence to the Patriarch ' s camp resulted from his ambition : Apokaukos sought further advancement by trying to convince Kantakouzenos to declare himself Emperor . When the latter refused , Apokaukos secretly switched his allegiance . In Donald Nicol ' s opinion , had Kantakouzenos remained at Constantinople , his authority might have remained secure . As the " megas domestikos " and regent however , he had the duty of dealing with the Empire ' s various enemies , who sought to take advantage of Andronikos ' death . Dushan had invaded Macedonia , the Emir of Saruhan raided the coasts of Thrace , and Tsar Ivan Alexander of Bulgaria threatened war . In July Kantakouzenos left the capital at the head of the army , leaving control of the government to Apokaukos , whom he still believed loyal to him . Kantakouzenos ' campaign proved successful . He persuaded Dushan to withdraw and repulsed the Turkish raiders , while Ivan Alexander , threatened by a fleet from the Emirate of Aydin , renewed his peace treaty with Byzantium . To crown this success , Kantakouzenos received an embassy of the Latin barons of the Principality of Achaea in the Morea . They expressed readiness to surrender the country in exchange for a guarantee of their property and rights . It was a unique opportunity , as Kantakouzenos himself recognized in his memoirs , since if successful , the Catalan - controlled Duchy of Athens was bound to follow , consolidating Byzantine control over Greece . At this point Kantakouzenos received grave news from Constantinople . In late August Apokaukos attempted a coup and tried to kidnap John V . Having failed , he fled to his fortified house at Epibatai , where he was blockaded by troops . Kantakouzenos returned to Constantinople in early September , where he stayed for a few weeks consulting with the Empress . On his way back to Thrace to prepare for a campaign into the Morea , he went to Epibatai , where he pardoned Apokaukos and restored him to his former offices . Outbreak of the war : Autumn 1341 . Kantakouzenos ' second departure proved a great error . Back in the capital , his enemies moved in his absence . Apokaukos gathered a group of high - ranking aristocrats around him , including men such as the " megas droungarios " John Gabalas or George Choumnos , whom he tied to himself by marriage alliances . The Patriarch , backed by Apokaukos ' group and the authority of the Empress , dismissed Kantakouzenos from his offices and declared him a public enemy . Kalekas himself was proclaimed regent and Apokaukos named Eparch of Constantinople . Kantakouzenos ' relatives and supporters were imprisoned or forced to flee the city , and their properties confiscated . Although Kantakouzenos ' wife and children were safe in his headquarters at Demotika ( Didymoteicho ) , the regency placed his mother , Theodora , under house arrest . The privations she suffered during her imprisonment were to cause her eventual death . As the first groups of his partisans fleeing the capital arrived at Demotika , Kantakouzenos , by his own account , tried to negotiate with the new regency , but his approach was rebuffed . Finally forced to take decisive action , on 26 October 1341 , the army ( 2 , 000 cavalry and 4 , 000 infantry , according to Gregoras ) and his supporters , largely drawn from the land - holding aristocracy , proclaimed Kantakouzenos Emperor . Although he still presented himself officially as a junior colleague to John V , and claimed to be only acting in the boy ' s name , having staked his claim on the throne , he had effectively started a civil war . Kantakouzenos still hoped that negotiation might resolve the situation , but all his envoys were imprisoned and he and his supporters excommunicated by Patriarch John XIV . On 19 November 1341 , the regency responded to Kantakouzenos ' proclamation as Emperor with the formal coronation of John V . Reaction to Kantakouzenos ' proclamation caused a rift in Byzantine society , with the rich and powerful land - holding magnates ( traditionally called the " dynatoi " , the " powerful ones " ) who dominated the countryside quickly rallying to support him , while the ordinary population , often living in abject conditions and suffering under oppressive taxation , supported the Empress - dowager and the Patriarch . Apokaukos was especially quick to capitalize upon this division and foment popular dislike for the aristocracy , by widely publicizing the immense wealth confiscated from Kantakouzenos ' and his supporters ' houses and estates . In the words of Donald Nicol , " it was against him [ Kantakouzenos ] and everything that he stood for as a millionaire and landowning aristocrat that the people rose up . ' Kantakouzenism ' became their war cry , the slogan of their discontent " . Thus the battle lines of the civil war were drawn up between urban and rural factions . The cities , dominated by the middle - class civil bureaucracy and merchant class ( the " people of the market " ) , favoured a more mercantile economy and close relations with the Italian maritime republics , while the countryside remained under the control of the conservative landed aristocracy , which derived its wealth from its estates and traditionally shunned commercial and entrepreneurial activities as unworthy of its status . The lower social strata tended to support the respective dominant faction , the middle classes in the cities and the landholding magnates in the countryside . Polarization of this nature was not new in the Byzantine Empire . Evidence of competition between the landed aristocracy and the city - based middle classes in the political , economic and social spheres has been attested since the 11th century , but the scale of the conflict that erupted in 1341 was unprecedented . This class conflict was mirrored in the breakaway Byzantine Empire of Trebizond , as well , where a pro - imperial and pro - Constantinopolitan urban faction confronted the provincial landholding aristocracy between 1340 and 1349 . The more conservative and anti - Western tendencies of the aristocrats , and their links to the staunchly Orthodox and anti - Catholic monasteries , also explain their increased attachment to the mystical Hesychasm movement advocated by Gregory Palamas , whose views were mostly opposed in the cities . Although several significant exceptions leave the issue open to question , in the contemporary popular mind ( and in traditional historiography ) , the supporters of " Palamism " and of " Kantakouzenism " were usually equated . Kantakouzenos ' eventual victory also meant the victory of Hesychasm , confirmed in a synod in Constantinople in 1351 . Hesychasm became a hallmark of the Orthodox church tradition , although it was rejected by the Catholics as a heresy . The first manifestation of this social division appeared in Adrianople where , on 27 October , the populace expelled the city ' s aristocrats , securing it for the regency . This event was repeated over the next weeks in town after town throughout Thrace and Macedonia , as the people declared their support for the regency and against the despised forces of " Kantakouzenism " . In this hostile atmosphere , many of Kantakouzenos ' soldiers abandoned him and returned to Constantinople . In Demotika alone the popular uprising was quelled , and the town remained Kantakouzenos ' main stronghold in Thrace throughout the war . Kantakouzenos seeks Dushan ' s aid : 1342 . When heavy snowfall rendered campaigning impossible during the following winter , Kantakouzenos instead sent envoys , including an embassy of monks from Mount Athos to Constantinople . However , they too were dismissed by the Patriarch . By then , almost all of the Byzantine provinces and their governors had declared themselves for the regency . Only Theodore Synadenos , an old associate of Kantakouzenos who was the governor of the Empire ' s second city , Thessalonica , indicated his support . Synadenos had kept his allegiance to Kantakouzenos secret from the city ' s populace , and intended to surrender Thessalonica in collusion with the local aristocracy . Furthermore , Hrelja , the Serbian magnate and virtually independent ruler of Strumica and the Strymon River valley , seemed to lean towards Kantakouzenos . Consequently , as soon as the weather improved , on 2 March 1342 , Kantakouzenos left his wife Irene Asanina , his brother - in - law Manuel Asen and his daughters to hold Demotika and marched west with his army toward Thessalonica . On the way , he first attacked Peritheorion but was repelled and continued westward . Kantakouzenos was however able to take fortress Melnik , where he met with Hrelja to forge an alliance . Their two armies marched toward Thessalonica , but arrived too late to take control . As they approached the city , they were met by Synadenos and other aristocrats , who had fled after an uprising led by a radical popular party , the Zealots . Soon afterwards a fleet of 70 ships led by Apokaukos reinforced the city . Synadenos , whose family had remained behind in Thessalonica , defected to the regency . Apokaukos ' son John was appointed governor of Thessalonica , although effective power rested with the Zealots , who for the next seven years led an autonomous regime unparalleled in Byzantine history . At the same time , the regency ' s army campaigned in Thrace , formally taking possession of towns secured by popular revolt . With Thessalonica barred against him , his supply lines to Thrace cut , and desertions having reduced his army to 2 , 000 men , of whom half belonged to Hrelja , Kantakouzenos was forced to withdraw north to Serbia , where he hoped to secure the aid of Stephen Dushan . Soon after , Hrelja also deserted Kantakouzenos and joined the regency , hoping to gain control of Melnik for himself . In July 1342 , Kantakouzenos met Dushan near Pristina . The Serbian ruler appeared initially reluctant to form an alliance . Nevertheless , under pressure from his nobles , especially the powerful Jovan Oliver , he could not afford to miss this unique opportunity to expand south . Desperately in need of Serbian aid , Kantakouzenos apparently agreed that the Serbs could keep any town they took , despite his own later account to the contrary . According to Nikephoros Gregoras , the Serbs claimed all of Macedonia west of Christopolis ( Kavala ) , except for Thessalonica and its environs . The only concession Kantakouzenos secured was that an exception be made for those towns that surrendered to him in person . To seal the pact , Kantakouzenos ' younger son , Manuel , was to be wed to the daughter of Jovan Oliver , although after Dushan later broke the alliance , the marriage did not take place . Hrelja too acceded to the pact , in exchange for the surrender of Melnik by Kantakouzenos ' garrison . After Hrelja ' s death later that year , Melnik was seized by Dushan . In late summer 1342 , Kantakouzenos , accompanied by several Serbian magnates , marched into Macedonia at the head of a Greek and Serbian force , intending to break through to his wife , who still held out at Demotika . His advance was stopped almost immediately before Serres when the city refused to surrender , and the subsequent siege had to be abandoned after an epidemic killed most of his men , forcing him to retreat into Serbia with a rump force of barely 500 soldiers . Dushan led a more successful parallel campaign , capturing Vodena ( Edessa ) . Serbian forces captured Florina and Kastoria shortly afterwards , thereby extending their hold over western Macedonia . The Serbs also expanded their control over Albania , so that by the summer of 1343 , with the exception of Angevin - controlled Dyrrhachium , all of the region appears to have fallen under Serbian rule . Morale among Kantakouzenos ' followers fell dramatically . Rumours circulated in Constantinople that a dejected Kantakouzenos planned to retire to Mount Athos as a monk , and riots broke out in the city in which several rich men were killed and their houses looted by the populace . In late fall , Empress Anna twice sent embassies to Dushan trying to convince him to surrender Kantakouzenos , but the Serbian ruler , seeking to extract more profit from their alliance , refused . Kantakouzenos ' fortunes began to improve when a delegation of the nobles of Thessaly reached him and offered to accept his authority . Kantakouzenos appointed his relative John Angelos as the province ' s governor . Although in effect a semi - independent ruler , Angelos was both loyal and effective . He soon brought Epirus — which he had governed in Andronikos II ' s name in 1340 — into the Kantakouzenist camp , and even made gains in Thessaly at the expense of the Catalans of Athens . Another effort by Kantakouzenos to break from Serbia into Macedonia failed before Serres . In the meantime , Kantakouzenos ' wife Irene called upon the aid of the Bulgarians to help relieve the blockade of Demotika by the regency ' s army . Ivan Alexander dispatched troops , but although they clashed with the regency ' s forces , they made no effort in assisting the city , instead pillaging the countryside . Kantakouzenos resurgent : 1343 – 1345 . At this point , Kantakouzenos ' position was greatly strengthened by the intervention of his old friend , Umur Bey , who in late 1342 or early 1343 sailed up the Evros river with a fleet of 300 ships and 29 , 000 ( according to Kantakouzenos ) or 15 , 000 ( according to Turkish sources ) men - in - arms and relieved Demotika both from the siege by the regency ' s forces and from the depredations of the Bulgarians . After pillaging Thrace for a few months , Umur was forced to retreat to Asia at the onset of winter , to which the Turks were unaccustomed . This turn of events displeased Dushan , for Kantakouzenos now had an independent power base and was less reliant on the Serbian ruler ' s goodwill . The final rift between Kantakouzenos and Dushan occurred in April 1343 , when Kantakouzenos persuaded the town of Berroia , besieged by the Serbs , to surrender to him instead of Dushan . This was followed by the surrender of several other forts in the area to Kantakouzenos , including Servia and Platamon . These moves strengthened Kantakouzenos ' position and independence from Dushan , thereby thwarting the latter ' s plans for expansion . Realizing that he had little to gain by continuing to support Kantakouzenos , Dushan opened negotiations with the regency and concluded a formal alliance with them in the summer of 1343 . Meanwhile , Kantakouzenos and his army camped outside Thessalonica , hoping to take the city through the aid of his supporters within the walls . Apokaukos arrived at the head of the Byzantine fleet to aid the Zealots , pinning Kantakouzenos down in Macedonia between Thessalonica and Dushan ' s possessions . Once again Umur of Aydin came to Kantakouzenos ' assistance with a fleet carrying some 6 , 000 men , whereupon Apokaukos and his ships fled from the superior Turkish navy . Nevertheless , a reinforced Thessalonica was able to hold out against a siege by Kantakouzenos and Umur . Although he had failed to take Thessalonica , the presence of his Turkish allies allowed Kantakouzenos to turn his attention towards Thrace . In late 1343 he left his son Manuel as governor of Berroia and western Macedonia and marched towards Demotika , relieving the city and seeing his wife for the first time in almost two years . On his way to Demotika , Kantakouzenos had seized a number of fortresses in Thrace , although another siege of Peritheorion failed . He followed up with a successful campaign that took Komotini and other fortresses in the Rhodope area . Over the next couple of years , the towns and forts of Thrace came over to Kantakouzenos ' camp one by one , but at great cost , as his mainly Turkish troops repeatedly plundered the countryside . The shifting tide of the war did not go unnoticed in the opposing camp . In late 1344 , several prominent personalities defected to Kantakouzenos , including John Vatatzes , a general and relative by marriage to both the Patriarch and Apokaukos , the Patriarch of Jerusalem Lazaros , and , most importantly , Manuel Apokaukos , son of the " megas doux " and governor of Adrianople . At the same time , the regency ' s alliance with Dushan was paying dividends for the Serbian ruler alone , as he had free rein to plunder and occupy all of Macedonia and Epirus . By the end of 1345 , only Thessalonica , held by the Zealots , Serres and the surrounding region , which remained loyal to the regency , along with Berroia , which still held out under Manuel Kantakouzenos , remained outside Serbian control . These developments placed the regency in considerable difficulties . In spite of Apokaukos ' adroit management of the state ' s finances , the devastation caused by the prolonged wars had emptied the treasury . In August 1343 , Empress Anna was forced to pawn the crown jewels to Venice for 30 , 000 ducats . In addition , Turkish ravages in Thrace led to a scarcity of food in Constantinople . Hoping for Western aid , Anna appealed to the Pope , promising the submission of herself , John V , Apokaukos and even the Patriarch to his authority , and began persecuting the pro - Kantakouzenists and anti - Western Palamists . In 1344 , the regency concluded a further alliance with Bulgaria , which required the surrender of Philippopolis ( Plovdiv ) and nine other towns in northern Thrace along the river Evros . Nevertheless , after their occupation , Ivan Alexander refrained from direct action against Kantakouzenos ' forces operating in southern and eastern Thrace . At the same time , Momchil , a former brigand whom Kantakouzenos had entrusted with control over the region of Merope in the Rhodope mountains , switched over to the regency . In early 1344 , Kantakouzenos was deprived of Umur and the bulk of his army , who had sailed home to repel a Latin attack on his main harbour , Smyrna . On their way , the Turkish force was attacked by the Serbs under Gregory Preljub , but prevailed at the Battle of Stephaniana . Nevertheless , Kantakouzenos was able to ward off joint attacks by Dushan and Apokaukos until Umur returned to his aid the next spring at the head of an army of 20 , 000 men . Kantakouzenos and Umur raided Bulgaria , and then turned against Momchil . The latter had exploited the power vacuum in the Rhodope , an effective no man ' s land between the Serbs , Bulgarians and Byzantines , to set himself up as a quasi - independent prince , supported by a substantial force of around 5 , 000 men . On 7 July 1345 , the two armies clashed at Peritheorion . Momchil ' s army was crushed , and he himself fell in the field . Soon afterwards , Dushan arrived before Serres and laid siege to the city . Rejecting demands by Kantakouzenos to withdraw , a clash appeared inevitable until the murder of Alexios Apokaukos in Constantinople forced Kantakouzenos to direct his attention there . Last years of the war : 1345 – 1347 . In early 1345 , Kantakouzenos sent Franciscan monks to the regency to make an offer of conciliation , but it was rejected . Despite this show of confidence , the regency ' s position remained insecure . The defections of the previous winter had weakened their control of the capital , and in response Apokaukos launched a series of proscription s . He also ordered the construction of a new prison to house political prisoners . On 11 June 1345 , while undertaking an inspection of the prison unaccompanied by his bodyguard , Apokaukos was lynched by the prisoners . When Kantakouzenos heard the news he marched towards Constantinople , urged by his supporters , who expected that the death of Apokaukos would result in the collapse of the regency . Kantakouzenos was more sceptical , and indeed the Patriarch and Empress Anna quickly brought the situation under control . At the same time , Kantakouzenos suffered a series of reverses . These began when John Apokaukos , the nominal governor of Thessalonica , openly announced his allegiance to Kantakouzenos and his plans to surrender the city . He was immediately thwarted by the Zealots who rose up again and killed Apokaukos and the other Kantakouzenist sympathizers in the city . Then John Vatatzes , who had defected to Kantakouzenos the year before , once more switched sides . He attempted to take some of Kantakouzenos ' Turkish allies and a few Thracian cities with him , but was murdered soon afterwards . Finally , Kantakouzenos lost the support of his most crucial ally , Umur of Aydin , who left with his army to confront the crusaders in Smyrna . Kantakouzenos replaced him by allying himself with the Emir of Saruhan and , more importantly , Orhan I of the rising Ottoman emirate in Bithynia . In September 1345 , after a long siege , Serres fell to Dushan . The Serbian ruler , who by now controlled about half of the pre - 1341 Byzantine realm , was spurred by this success to lay his own claim on the Byzantine throne . Consequently , on Easter Sunday , 16 April 1346 , he was crowned " Emperor of the Serbs and the Romans " in Skopje , thereby founding the Serbian Empire . This development prompted Kantakouzenos , who had only been acclaimed Emperor in 1341 , to have himself formally crowned in a ceremony held at Adrianople on 21 May , presided over by the Patriarch of Jerusalem , Lazaros . Lazaros then convened a synod of bishops to excommunicate the Patriarch of Constantinople , John Kalekas . Not long afterwards , Kantakouzenos ' ties with his new ally Orhan were cemented through the marriage of his daughter Theodora Kantakouzene to the Ottoman emir at an elaborate ceremony in Selymbria . For the regency , the situation had become desperate . Empress Anna ' s requests for aid from foreign powers proved unsuccessful , as both Orhan and the beylik of Karasi rebuffed her overtures for assistance . Only Balik , the ruler of Dobruja , sent an elite force of 1 , 000 men under his brothers Theodore and Dobrotitsa , but they were routed by Kantakouzenos ' " protostrator " George Phakrases . The emirate of Saruhan offered a more substantial force of 6 , 000 men in the summer of 1346 , but instead of fighting , they plundered Thrace and then defected to join Kantakouzenos ' army . Revenue remained scarce for the regency , the Genoese once again seized the imperial possessions of Chios and Phocaea , and on 19 May 1346 , a part of the Hagia Sophia cathedral collapsed , a terrible omen in the eyes of the capital ' s inhabitants . By the summer of 1346 , Kantakouzenos stood on the verge of victory . He left Thrace under the control of his son Matthew and moved on to Selymbria , close to Constantinople . He did not attack the capital , but waited for almost a year for the city to surrender . In his memoirs , he explains that he did not want to turn his Turks on the city , although contemporaries such as Gregoras accused him of indecision and of needlessly prolonging the war . As the months passed , and the privations in Constantinople increased , the pro - Kantakouzenos faction in the capital grew as the Empress refused even to consider negotiations . Twice agents were sent to assassinate Kantakouzenos , but they failed . The Empress eventually fell out with Patriarch John Kalekas , who was deposed in a synod on 2 February 1347 . On the same night , supporters of Kantakouzenos opened the disused Golden Gate , and Kantakouzenos entered the city with 1 , 000 men . Meeting no resistance , his troops surrounded the Palace of Blachernae , the imperial residence , the next morning , but the Empress refused to surrender for several days , still fearful of the fate that awaited her . Kantakouzenos ' men grew impatient and stormed part of the palace complex , and John V persuaded his mother to accept a settlement . Peace settlement and Kantakouzenos ' reign . On 8 February 1347 , the war formally ended with an agreement making Kantakouzenos senior emperor for ten years , after which he and John V would reign as equals . Kantakouzenos also promised to pardon anyone who had fought against him . To seal the pact , John V married Kantakouzenos ' daughter Helena , and in May , Kantakouzenos was crowned again in the Church of St . Mary of Blachernae . In the end , as Donald Nicol commented , the long conflict had been meaningless , with terms that " could have been agreed five years before and saved the Empire so much bitterness , hatred and destruction . " Despite the moderation and clemency shown by Kantakouzenos in this settlement , it did not gain universal acceptance . Supporters of the Palaiologoi still distrusted him , while his own partisans would have preferred to depose the Palaiologoi outright and install the Kantakouzenoi as the reigning dynasty . Kantakouzenos ' eldest son , Matthew , also resented being passed over in favour of John V , and had to be placated with the creation of a semi - autonomous appanage covering much of western Thrace , which doubled as a march against Dushan ' s Serbia . Of the remaining Byzantine territories , only the Zealots in Thessalonica , now an isolated exclave surrounded by the Serbs , refused to acknowledge the new arrangement , instead leading a " de facto " independent existence until Kantakouzenos conquered them in 1350 . After 1347 , John VI Kantakouzenos tried to revive the Empire , but met with limited success . Aided by the depopulation brought by about by the Black Death , Dushan and his general Preljub took Kantakouzenos ' Macedonian strongholds as well as Epirus and Thessaly in 1347 – 1348 , thereby completing their conquest of the remaining Byzantine lands in mainland Greece . An attempt to break Byzantium ' s dependence for food and maritime commerce on the Genoese merchants of Galata led to a Byzantine – Genoese war , which ended in 1352 with a compromise peace . In 1350 , Kantakouzenos took advantage of Dushan ' s preoccupation with a war against Bosnia to recover Thessalonica from the Zealots as well as Berroia , Vodena and other Macedonian cities from the Serbs , but the Serbian emperor quickly reversed the Byzantine gains . Again , only Thessalonica remained in Byzantine hands . Steadily deteriorating relations between Matthew Kantakouzenos , who now ruled eastern Thrace , and John V Palaiologos , who had taken over Matthew ' s former domain in western Thrace , sowed the seeds of yet another internal conflict . Open warfare broke out in 1352 , when John V , supported by Venetian and Turkish troops , launched an attack on Matthew Kantakouzenos . John Kantakouzenos came to his son ' s aid with 10 , 000 Ottoman troops who retook the cities of Thrace , liberally plundering them in the process . In October 1352 , at Demotika , the Ottoman force met and defeated 4 , 000 Serbs provided to John V by Stephen Dushan . This was the Ottomans ' first victory in Europe and an ominous portent . Two years later their capture of Gallipoli marked the beginning of the Ottoman conquest of the Balkans , culminating a century later in the Fall of Constantinople . Meanwhile , John V fled to the island of Tenedos , from where he made an unsuccessful attempt to seize Constantinople in March 1353 . John VI Kantakouzenos responded by having Matthew crowned as co - emperor , but John V Palaiologos , enlisting Genoese support and relying on the declining popularity of Kantakouzenos , succeeded in entering the capital in November 1354 . John VI abdicated and retired to a monastery . Matthew held out in Thrace until 1357 , when he too abdicated , leaving John V Palaiologos as the sole master of a rump state . Consequences of the civil war . The civil war proved a critical turning point in the history of the Byzantine Empire . In the words of the Byzantinist Angeliki Laiou , " after the end of the second civil war , Byzantium was an empire in name only " , while according to Eva de Vries - Van der Velden , it marks " the point of rapture between the " decline " and " the fall " of the Byzantine Empire " . The Byzantines ' division and reliance on foreign troops , especially the Serbs and Turks , encouraged the latter ' s expansionism . Dushan in particular proved adept in exploiting the civil war to expand his state at Byzantium ' s expense . Aside from huge territorial losses , the prolonged conflict exhausted the Byzantine state ' s resources . Thrace , the largest contiguous territory remaining in the Empire , suffered such devastation that , along with Constantinople , it became dependent on grain imported from Bulgaria and the Crimea . Trade had stopped , and the treasury contained , in the words of Gregoras , " nothing but the atoms of Epicurus . " Kantakouzenos had exhausted his own personal fortune , and Empress Anne had left the Empire heavily indebted to the Venetians . The war also led to the collapse of the centralized imperial administration in the provinces , causing control of the Thracian countryside to shift to a manorial system run by the local magnates . Despite their considerable wealth , the magnates , through exemptions or outright evasion , managed to avoid paying taxes to the imperial government . In addition , the arrival in 1347 of the Black Death and its recurrent outbreaks further reduced the Empire ' s tax and recruitment base , curtailing its ability to reverse the Serbian territorial gains . Along with the renewal of the civil war in 1352 , these factors , with the plague foremost , destroyed any chance of even a modest recovery similar to that experienced under Andronikos III . Thereafter , Byzantium remained under the menacing threat of stronger neighbours , unable to pursue an independent foreign policy , handicapped by a shortage of resources and riven by internal strife . Nevertheless , through a combination of fortuitous external circumstances and adroit diplomacy , it survived for another century , until finally conquered by the Ottomans in 1453 . Only the Byzantine exclave in the Morea remained prosperous , having been spared the ravages of the civil war because of its relative isolation . The appointment of Manuel Kantakouzenos as its " despotes " in 1349 heralded the creation of the semi - independent Despotate of the Morea , which experienced the last economic and cultural flowering of the Byzantine world before it too fell to the Ottomans in 1460 .