Byzantine civil war of 1352–57

Part of the Byzantine civil wars, the Byzantine–Serbian wars and the Byzantine–Turkish wars

Date	1352–1357
Location	Thrace and Constantinople
Result	John V Palaiologos becomes sole ruler, deposes the Kantakouzenoi

Belligerents

John V Palaiologos
Allies:

Serbian Empire

Republic of Venice

Republic of Genoa

John VI Kantakouzenos

Matthew Kantakouzenos
Allies:

Ottoman emirate

The Byzantine civil war of 1352–1357 marks the continuation and conclusion of a previous conflict that lasted from 1341 to 1347. It involved John V Palaiologos against the two Kantakouzenoi, John VI Kantakouzenos and his eldest son Matthew Kantakouzenos. John V emerged victorious as the sole emperor of the Byzantine Empire, but the resumption of civil war completed the destruction of the previous conflict, leaving the Byzantine state in ruins.

In the aftermath of the 1341–1347 conflict, John VI Kantakouzenos had established himself as senior emperor and tutor over the young John V Palaiologos. This state of affairs however was not destined to last; 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 the new Serbian Empire of Stephen Dushan.

Steadily deteriorating relations between Matthew Kantakouzenos, who now ruled eastern Thrace, and John V Palaiologos, who resided in western Thrace, sowed the seeds for the resumption of the civil war.

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 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.

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