A relative of the statesman and emperor John VI Kantakouzenos, he took the latter's side in the Byzantine civil war of 1341–1347 and in late 1342 received the governorship of Thessaly (and possibly Epirus), which he held until his death in 1348.
[7] Byzantine rule was generally resented by the local populace,[8] and in 1339 a revolt broke out in Epirus, which quickly gained ground and succeeded in taking a few key fortresses, including the capital, Arta.
Later in the same year, John Angelos was sent by Andronikos III along with the governor of Thessaly, Michael Monomachos, as the vanguard of the Byzantine army into Epirus.
The rebels avoided a pitched battle and retired to the fortresses, which one by one fell after sieges or through negotiations, so that the region was subdued by the end of the year.
[10] In spring 1342, Angelos followed Kantakouzenos in his abortive campaign to Thessalonica and his subsequent flight to Serbia and the court of its ruler Stephen Dushan (r.
Although Angelos was later raised to the high rank of sebastokrator and enjoyed a measure of autonomy, his authority was circumscribed: the post was not hereditary, and he functioned strictly as the emperor's deputy.
Taking advantage of the decline of the Catalans of the Duchy of Athens, he made gains in the south, and even managed to extend his authority over Epirus and Acarnania as well, where he seized and placed under house arrest Anna Palaiologina, the scheming widow of John II Orsini and sister of Angelos's own wife.