The Turks exploiting the weakness of the Byzantine state and the oppositions between the Balkan populations, gradually entered the area of Macedonia and Balkan and surrounded Thessalonica. The city, after a lot of adventures was conquered by the Turks of Mourat A' (1387), and escaped from its dictators in 1403.
When the Turkish threat became dangerous later again, the despot of Thessalonica Andronikos and the sovereigns of Thessalonica granted the city to the Venetians (1423) with terms that aimed at its salvation. However it quickly developed in a new dictatorship.
On March 1430, Thessalonica after a siege fell almost in the hands of Turks of Mourat B', in order to begin a period of long-lasting work and callous oppression. The Turks destroyed almost the entire city. Thessalonica was depopulated by its residents, while thousands of captives, were led in the slave bargains of the east. The main Byzantine temples of the city were converted in "mosques".