How a dynastic struggle in Byzantium paved the way for the Ottoman conquest of Europe
The Byzantine civil war of 1352–1357 began as a power struggle between Emperor John V Palaiologos and John VI Kantakouzenos. While John V eventually emerged as sole ruler, the conflict shattered the empire, inviting foreign intervention that fundamentally altered the course of history in the Balkans and beyond.
Following the earlier civil war of 1341–1347, John VI Kantakouzenos acted as senior emperor and tutor to the young John V Palaiologos. This arrangement was inherently unstable, as supporters of the Palaiologoi remained deeply suspicious of Kantakouzenos, while his own faction pushed for the total displacement of the Palaiologoi dynasty. Tensions were further exacerbated by the ambitions of Matthew Kantakouzenos, the eldest son of John VI, who resented his secondary status. To manage these rivalries, Matthew was granted a semi-autonomous appanage in western Thrace, intended to function as a defensive march against the expanding Serbian Empire of Stephen Dushan.
Open hostilities erupted in 1352 when John V attacked Matthew. John VI intervened with 10,000 Ottoman troops, who proceeded to plunder Thracian cities. In October 1352, at Demotika, these Ottoman forces defeated 4,000 Serbian soldiers provided to John V by Dushan. This engagement marked the first Ottoman victory on European soil. The strategic consequences were profound; two years later, the Ottoman capture of Gallipoli initiated a campaign of conquest that would eventually culminate in the fall of Constantinople a century later. Meanwhile, internal Byzantine politics remained volatile, with John V attempting to seize the capital in March 1353 before finally succeeding in November 1354, forcing John VI to abdicate and enter a monastery.
The conflict persisted through Matthew, who continued to challenge the new order from Thrace. In 1356, he mobilized an army of 5,000 Turks to attack Serres, the capital held by the Serbians. The following year, in 1357, a Serbian relief force led by Vojin, Count of Drama, defeated the Turks. Matthew was captured and held until John V paid his ransom. Ultimately, Matthew was permitted to join his brother Manuel in the Morea. John V remained the sole master of a state that had been left in ruins, its infrastructure and stability decimated by years of internal warfare and the reliance on foreign mercenaries.
Source: Byzantine civil war of 1352–1357
