Ottoman expansion into the Balkans was accompanied by two systematic instruments of population policy. Sürgün was the compulsory transfer of populations by imperial decree: Turkmen and nomadic groups from Anatolia were moved into newly conquered Balkan districts to secure them, and Balkan populations were moved in the other direction; the practice was later used on a large scale to repopulate Istanbul after 1453. The devşirme was a periodic levy of Christian boys, chiefly from Balkan villages, who were taken from their families, converted to Islam, and trained for the Janissary corps or the palace service, from which the highest offices of the empire were filled. The characterisation of the devşirme is disputed: Ottoman-centred scholarship, notably Halil İnalcık's, presents it as a recruitment mechanism that gave peasant boys access to the empire's highest positions, while Balkan and much Western scholarship treats it as a tribute in children taken by force from subject communities; both descriptions rest on the same evidence of compulsion and of subsequent careers.
The Ottoman state compulsorily resettled Anatolian Muslim and nomadic populations into the conquered Balkans, moved Balkan populations into Anatolia, and levied Christian boys from Balkan villages for conversion and service to the sultan
No denominator can be reconstructed for this window. The Ottoman tahrir registers that would allow one begin only in the later fifteenth century, after the period covered here; V. L. Ménage and later scholars estimate the devşirme took on the order of 1,000-3,000 boys a year from the Balkan Christian villages, but the sürgün resettlements moved whole households in numbers never centrally totalled, across territories whose populations were changing hands throughout.
Neither sürgün nor devşirme was lethal by design and no death toll is associated with them. They were instruments for moving and appropriating populations, and the sources record transfers and levies rather than killing.
The compulsory levy of Christian boys from their families for conversion and state service is documented in Ottoman kanunname legislation and levy registers and described in the Cambridge History of Turkey.
Turkey, Bulgaria