In his memoirs Grivas described X as a resistance movement. In fact, its members were armed by the British and there is evidence that information about German positions and troop movements were sent by X to the Allies in Egypt. However, towards the end of the German occupation, the organisation's aim shifted to combating the communist resistance movements of EAM / ELAS whose goal of taking over Greece after liberation was becoming evident. During the occupation, X's influence was small, confined to certain neighbourhoods of Athens. Thanks to British aid, however, the organisation became increasingly more powerful. After the Germans left, Organisation X fought ELAS at the Theseum area of Athens on December 4, 1944. The ensuing battle was costly to both sides. Grivas would later claim that he only had 80 men at his disposal at the Theseum though it is possible that his fighters were joined by policemen or others of similar political views.
On the nationalist side, Organisation X is viewed as a patriotic organisation that helped the resistance and prevented the Communists from taking over Athens by force, however, communists have claimed that X was a "fascist" organisation that had collaborated with the Nazis in order to exterminate them.