This chapter is based mostly on Czech achival materials in order to focus on so far unknown aspects of Czechoslovak involvement in the Greek Civil war, as well as its participation after the end of the war. Attention is paid to the role of StB in the establishment of the so-callied sabotage school for Greek communists during the period of 1950/1951, and the renewal of Czechoslovak participation in illegal missions of the KKE within Greece itself.