Diamandi was active in the Greek regions of Thessaly and Macedonia during World War II, supporting the Italian and German occupation forces and promoting the creation of an autonomous Vlach state, envisioned as a "Principality of the Pindus", a name also used for a similar attempt in 1917, in which Diamanti had also been involved. Calling himself a leader and "Representative of the Vlachs of the Lower Balkans", Diamanti established an organization under the name of "Roman Legion" and helped the Italian forces in the collection of weapons that the Greeks had hidden after the surrender of the Greek Army. Diamanti left Greece by the summer of 1942 for Romania and Nicholas Matousis, a Vlach lawyer, already active as second-in-command, replaced him in the organization. Another important figure in the Legion was the Aromanian Vasil Rapotika who was leading the paramilitary units. After action from several resistance groups in 1942 and the dynamic response of ELAS against members of the Legion, and the withdrawal of Italian forces, the Legion ceased to exist in September 1943, while Matousis fled to Athens. The fate of the leading figures and the members of the Legion:
Alcibiades Diamandi left for Romania in 1942, where he was later jailed when the Allies won and the new Communist government took power. He died in jail in Romania in 1948. In Greece he had been condemned to death from the Special Collaborationist Courts set up in 1945–47.
Nikolaos Matoussis also left Greece for Romania, one year later in 1943. He was also jailed and has been given to the hands of Greek authorities in 1964. In Greece, he started to serve his sentence, given to him in absentia, from the Special Treason Court after the war, but asked for re-trial and was found not guilty. He was released and in his civil rights were completely restored by a Greek court. Up to his death, in 1981, he lived in Athens.
Vassilis Rapotikas was captured by ELAS and was killed on the way to ELAS headquarters in end of May or on the beginning of June 1943
The members of the Roman Legion who did not flee to Romania were tried in the Treason Courts set up in 1945–47 and were sentenced. 617 people were accused, 152 were found guilty, 91 of which did not receive a sentence since they were already in prison sentenced for treason in other cases and for 55 there was no continuation due to their death. 319 were found innocent.
