In Thrace, more opposition was encountered. Before June 1941 and the German–Turkish Treaty of Friendship, the Germans did not allow Bulgarian civilian administration for fear of antagonizing Turkey with Bulgarian expansion; separate Greek, German, and Bulgarian occupation zones prevailed until August 1941. Thereafter, pressure was applied to Turkish inhabitants of the region to emigrate. The demographics of western Thrace had been changed by the 1921 population exchange between Greece and Turkey, with the arrival of many Greeks from East Thrace in the Turkish Republic and the departure of many Turks. Most villages were assigned to the Nevrokop diocese of the Bulgarian Church as part of a wider Bulgarization policy in education and religion. The Bulgarian school system was introduced in September 1941 and by 1942's end there were 200 new primary schools and 34 gymnasia established for ethnic Bulgarians alone; Turks and Greeks had separate schools, and despite protests of Muslim teachers, children of Pomaks were sent to Bulgarian schools organized on Orthodox Christian lines. Also in September 1941, the suppression of the Drama uprising against Bulgarian rule on the night of the 28-'9 September resulted in the deaths of around 1,600 people.