After completing his compulsory military service, he was sent to internal exile to the islands of Sifnos and Kimolos, along with fellow KKE members Miltiadis Porfyrogenis, Chrysa Hatzivasileiou, and Petros Rousos.

Karagiorgis returned to Athens, where he played a major role in the Party's underground press and the mobilization of civil servants.

Throughout the subsequent period until the end of the Axis occupation of Greece, he was the senior KKE and EAM official in Thessaly.

[1] After the outbreak of the Greek Civil War and the closing of Rizospastis, he fled Athens to the mountains of Thessaly, where he joined the Communist-run Democratic Army of Greece (DSE).

Heavily wounded in action, he was sent to Hungary to be operated on, and on his return was made a member of the communists' "Mountain Government" as Minister for War Supply (April 1949).