 However, during the interwar years, the ethnic composition of the region's population had been dramatically changed, as Greek refugees from Anatolia settled in Macedonia and Thrace following the population exchange between Greece and Turkey.This meant that only a small minority of Slavic-speakers could be lured to collaborate with the occupiers.Because of the harsh occupation policies, armed resistance in the Bulgarian zone was fierce and enjoyed almost universal support from the civilians; Greek guerrilla leaders such as Antonis Fosteridis engaged the Bulgarian military in many battles, and even penetrated into Bulgaria proper, raiding villages and capturing booty.