linguistic:translation
Byzantine civil war and vassalage: 1371–1394

By now the Ottomans had essentially won the war; Byzantium was reduced to a few settlements other than Constantinople and was forced to recognize its vassal status to the Ottoman Sultan. This vassalage continued until 1394. However, whilst Constantinople had been neutralized, the surrounding Christian powers were still a threat to the Ottomans and Asia Minor was not under complete Ottoman control. The Ottomans continued their thrust into the Balkans, proving to be great conquerors in Europe as they were in Anatolia; in 1385 Sofia was captured from the Bulgarians and Niš was taken the following year. Meanwhile, various smaller states were subjugated as vassals, including the Serbs following the Battle of Kosovo in 1389, much of Bulgaria was taken in 1393 by Bayezid I. By 1396 the Bulgarians had been entirely subjugated when Vidin fell.

Ottoman advances into the Balkans were aided by further Byzantine civil conflict – this time between John V and his eldest son Andronikos IV. With Ottoman aid from Murad I, John V was able to blind Andronikos IV and his son John VII Palaiologos in September 1373. Andronikos escaped with his son and secured Murad's aid by promising a higher tribute than John V's. The civil strife continued as late as September 1390 though potential for conflict continued until 1408. John V eventually forgave Andronikos IV and his son in 1381, angering his second son and heir apparent, Manuel II Palaiologos. He seized Thessalonika, alarming the Ottoman Sultan in liberating parts of Greece from Ottoman rule.

The death of Andronikos IV in 1385 and the capitulation of Thessalonika in 1387 to Hayreddin Pasha encouraged Manuel II Palaiologos to seek the forgiveness of the Sultan and John V. His increasingly close relationship with John V angered John VII who saw his right as the heir threatened. John VII launched a coup against John V but despite Ottoman and Genoese aid his reign lasted mere five months before he was toppled by Manuel II and his father.

In the year 1390, Bayazid I sent a fleet to burn down Chios and the surrounding market towns, Euboea, parts of Attica and the islands of the Archipelago. He destroyed every market town and village from Bithynia to Thrace on the outskirts of Constantinople and deported all the inhabitants.