The Organization of National Resistance of the Interior X (Greek: Οργάνωσις Εθνικής Αντιστάσεως Εσωτερικού Χ), commonly known as Organization X or simply X (Chi), was a resistance group formed during the Axis occupation of Greece, in June 1941. Its founder and leader was Georgios Grivas, lieutenant colonel of the Hellenic Army at the time and leader of the guerrilla campaign of Greek Cypriots against British colonial rule in the 1950s.
Initially, the group's name was Grivas' Military Organization (Greek: Στρατιωτική Οργάνωσις Γρίβα) and in March 1943 it was renamed, adopting the letter of the Greek alphabet chi.
The group had a nationalist, anticommunist and royalist orientation, and remained loyal to the Greek government in exile, headed by King George II. Its activities included intelligence, espionage, graffiti and sign writings, as well as assistance to Greeks who fled to the Middle East. As an armed group it was formed towards the end of the occupation, having purchased weapons from the retreating Germans, in order to prevent communist led EAM from assuming power in postwar Greece.
Organization X participated in the Dekemvriana (December 1944 events in Athens), suffering heavy casualties, on the side of the anti-EAM front that was led by the government of George Papandreou, after it had been disbanded and incorporated into the 143 Militia Battalion, which had its base in the neighborhood of Thisio. The most important battles that X took part in were the battle of Thisio and the battle of Makriyianni, where members of the group manned positions at Syngrou Avenue, thus relieving the gendarmerie force that was isolated in the barracks of the Gendarmerie Regiment.
Organization X was officially recognized as a National Organization of Internal Resistance by a royal decree of March 10 1950.[1]