During World War II, he fought as an artillery private of the
Hellenic Army at the
Albanian front against the Italian army, until the
German invasion in April 1941 and Greece's subsequent surrender and
occupation. After Germany's
offensive campaign in the
Soviet Union, the Greek Communist Party championed the creation of the
National Liberation Front (EAM), and Klaras was sent to
Central Greece (Greek Roumeli) to assess the potential for the development of a
guerrilla movement against the occupation forces in this area. His proposals were adopted by the party, and in January 1942, Klaras moved to the mountains to start setting up guerrilla groups. The first appearance of the
partisans organised by Klaras occurred on June 7, 1942, in the village of
Domnista in
Evrytania in Central Greece. There he presented himself as Major of Artillery (in hopes of gaining extra prestige among the villagers) with the nom de guerre of
Aris Velouchiotis (from
Ares, the Greek god of war, and
Velouchi, a local mountain) and proclaimed the existence of the
Greek People's Liberation Army (ELAS). Initially, he collected also the traditional local mountain
bandits in order to create a small group of experts in guerrilla fighting. Velouchiotis as a leader applied steely discipline and managed to have under his commands a considerable number of guerillas. Starting with only 15 men, ELAS' power finally comprised up to 50,000 guerillas. One of the most important early operations of the Greek resistance movement (in which Velouchiotis and his fighters, after negotiations with the British, agreed to participate alongside
Napoleon Zervas's republican
EDES resistance forces and twelve British
saboteurs under the leadership of Major
E. C. W. "Eddie" Myers) was the blowing-up of the
Gorgopotamos railway viaduct, south of Lamia, on November 25, 1942 (
Operation Harling). The destruction of the viaduct cut the single
Thessaloniki-
Athens rail line, thus the line connecting the
Balkans with southern Greece, but did not disrupt any supply lines—as would have been the case had it happened, as the British intended, two months earlier—to
Erwin Rommel's German forces in
Northern Africa, as it took place one month after the commencement of the
El Alamein battle on October 23, 1942, in which Rommel was badly defeated by the British. The destruction of the Gorgopotamos viaduct was to be the last operation where the communist-influenced ELAS organization fought alongside Greek Republican resistance forces, such as the
EKKA's
5/42 Evzones Regiment (military arm of EKKA) and EOEA (National Groups of Greek Guerillas,
Εthnikes Omades Ellinon Antarton, military arm of
EDES). But despite the signing of an agreement in July 1943 between the three main Resistance groups (EAM/ELAS, EDES and EKKA) to cooperate and to subject themselves to the Allied Middle East High Command under
General Wilson (the "
National Bands Agreement"), in the political field, the mutual mistrust between EAM and the other groups escalated. EAM-ELAS was by now the dominant political and military force in Greece, and EDES and EKKA, along with the British and the
Greek government-in-exile, feared that after the inevitable German withdrawal, it would try to dominate the country and establish a soviet regime. The rift ultimately led to a civil war in late 1943 and early 1944, in which ELAS attacked EDES, EOEA and destroyed EKKA's 5/42 Evzones Regiment, executing its leader Col.
Dimitrios Psarros. == Liberation and expulsion from Communist Party ==