On February 16, 1942, EAM gave permission to a communist veteran, Athanasios (Thanasis) Klaras (later known as Aris Velouchiotis) to examine the possibilities of an armed resistance movement, which led to the Greek People's Liberation Army (ELAS).

Initially, Velouchiotis also recruited traditional local mountain-living bandits, like Dimos Karalivanos, in order to create a small group of experts in guerilla warfare.

Their mission was to locate the guerrillas of EDES and their leader Napoleon Zervas, who were friendlier to the British Middle East Command than ELAS, and co-operate with them.

The destruction of the Gorgopotamos bridge was, along with the Norwegian heavy water sabotage in Rjukan, one of the two biggest guerrilla acts in occupied Europe[citation needed].

The blowing up of the bridge disrupted the German transportation of ammunition via Greece to Rommel's forces for several weeks, taking place at a time when the Afrika Korps in North Africa, retreating after the defeat of El Alamein, were in need of supplies.

In Central Greece, Aris Velouchiotis succeeded to form a powerful semi-conventional army which could attack German and Italian forces.

At the same time, some members of ELAS (Periklis, Tasos Leuterias, Diamantis, Nikiforos, Thiseas, Dimos Karalivanos, and Belis) have been distinguished during the battles.

The leadership of ELAS followed a triadic form, from its top down to platoon level: the captain (kapetánios), elected by the men and the overall leader of the unit, the military specialist (stratiotikós), usually a regular Army officer, responsible for tactical planning and training, and the political leader (politikós), usually a KKE member, as EAM's representative.

At its top, the General Headquarters of ELAS, these positions were filled by Aris Velouchiotis, Stefanos Sarafis and Andreas Tzimas (nom-de-guerre: Vasilis Samariniotis).

The second great event was the foundation of the United Panhellenic Organization of Youth (EPON) (Greek: Ενιαία Πανελλαδική Οργάνωση Νέων).

Two years after its foundation, ELAS' military strength had grown from the small group of fighters in Domnitsa to a force of some 50,000 partisans (estimates of the British government) or even as many as 85,000, according to EAM sources; EAM itself, and its associated organizations, had grown to a membership of anywhere from 500,000 to 750,000 (according to Anthony Eden) up to two million, in a country of 7.5 million inhabitants.

On 10 March 1944 the EAM-ELAS, now in control of most of the country, established the Political Committee of National Liberation (PEEA), widely known as the "Mountain Government" (Greek: Κυβέρνηση του βουνού, romanized: Kyvérnisi tou vounoú), in effect a third Greek government to rival the collaboration one in Athens and the government-in-exile in Cairo.

Its aims, according to its founding Act, were, "to intensify the struggle against the conquerors (...) for full national liberation, for the consolidation of the independence and integrity of our country (...) and for the annihilation of domestic fascism and armed traitor formations."

In October 1943 ELAS launched major attacks against EDES and the guerrilla group of Tsaous Anton in Northern Greece, precipitating a civil war across many parts of Greece which continued until February 1944, when the British agents in Greece negotiated a ceasefire (the Plaka agreement); ELAS broke the agreement by attacking the 5/42 Evzone Regiment, murdering the EKKA resistance group leader, Dimitrios Psarros, in as yet unclear and hotly debated circumstances and executing all the captives.

ELAS initially began to attack the National Republican Greek League (EDES) on accusations of collaboration with the Germans.

After the events of the Dekemvriana, ELAS was disarmed, though later some of its fighters (mostly KKE members) joined the Democratic Army during the civil war.

Translation Carrying my rifle on my shoulder, through cities, meadows, and villages, I clear the road for Freedom to come, laying for Her bay-leaves so She can pass.