Its military wing, the Greek People's Liberation Army (ELAS), quickly grew into the largest armed guerrilla force in the country, and the only one with nationwide presence.

At the same time, from late 1943 onwards, the political enmity between ΕΑΜ and rival resistance groups from the centre and right evolved into a virtual civil war, while its relationship with the British and the British-backed Greek government in exile was characterized by mutual mistrust, leading EAM to establish its own government, the Political Committee of National Liberation, in the areas it had liberated in spring 1944.

The organization reached its peak after liberation in late 1944, when it controlled most of the country, before suffering a catastrophic military defeat against the British and the government forces in the Dekemvriana clashes.

This marked the beginning of its gradual decline, the disarmament of ELAS, and the open persecution of its members during the "White Terror", leading eventually to the outbreak of the Greek Civil War.

The fact that a great many of the Communists in Greece had been tortured under the 4th of August Regime, and that the party had been heavily infiltrated by the secret police had contributed much to an embittered, paranoid view of the world.

On 16 July, however, the "National Workers' Liberation Front" (Εθνικό Εργατικό Απελευθερωτικό Μέτωπο, ΕΕΑΜ) was established, bringing the country's labour union organizations together.

ΕΑΜ's charter called for the "liberation of the Nation from foreign yoke" and the "guaranteeing of the Greek people's sovereign right to determine its form of government".

At the same time, while the door was left open to cooperation with other parties, the ΚΚΕ, with its large size concerning its partners, assumed a clearly-dominant position within the new movement.

[4] In 1941, the conditions of extreme poverty owing to the economic exploitation by the Axis occupation, most notably the Great Famine of 1941-42 together with the experience of defeat in April 1941 made many Greeks receptive to EAM's message.

[4] Before the 4th of August Regime was established in 1936, Greek politics were characterized by a "clientelist" system under which a politician, who was usually from a well-off family, would set up a patronage machine that would deliver goods and services in his riding in exchange for the votes of the local people.

Greek politicians jealously guarded control of their patronage machines, and vigorously resisted efforts to create better organized political parties as a threat to their own power.

[7] Starting under the 4th of August regime and even more so under the Triple occupation, the clientist system broke down as none of the politicians had the power to alter the policies carried out by the Bulgarians, Italians and Germans.

Much of EAM's appeal centered around the fact that it argued the people should mobilize and organize themselves to cope with the disastrous occupation, instead of passively hoping that one of the traditional politicians might be able to arrange some deal with the Germans to improve living conditions.

[8] The British historian David Close wrote: "EAM became a party unique in Greek history in achieving mass support while its leaders remained obscure".

But, since we felt so proud of winning, so...the feeling in the souls of the young people in Greece and of others, of everyone, was so enormous because of the victory of the Greeks up in the mountains of Epirus and in Albania, where they pushed the Italians out, abruptly, and without any declaration of war, that came later when they had crossed our border; the enthusiasm of the Greeks at that time was such that, and so great the heroism of the boys that were constantly leaving for the Albanian mountains to confront the enemy that had so underhandedly tried to cross the border.

Public knowledge of the plans created "a kind of pre-insurrectional atmosphere", which in February 1943 led to a mounting series of strikes in Athens, culminating in an ΕΑΜ-organized demonstration on 5 March, which forced the collaborationist government to back down.

ΕΑΜ even carried out elections to the PEEA's parliament, the "National Council", in April; for the first time in Greek electoral history, women were allowed to vote.

In the territories that it controlled, ΕΑΜ implemented its own political concept, known as laokratia (λαοκρατία, "people's rule"), based upon "self-administration, involvement of new categories (mainly women and youths) and popular courts".

[18] A recurring complaint before the war was the decision-making process in Athens was slow and indifferent to local opinion while EAM's system of "people's councils" was considered an improvement.

[18] Likewise, the legal system before the war was widely considered to be cumbersome and unfair in the sense that poor and illiterate farmers could not afford a lawyer nor understand the law, causing them to be victimized by those who did.

[26] Much of the work of the "People's Committees" was to mitigate the devastating effects of the Great Famine of 1941-42 and to carry out social reforms intended to ensure that everyone would receive food.

[26] There was constant tension between the demands of the national EAM leadership vs. the local "People's Committees" who often resisted orders to supply food to other villages in "Free Greece".

[28] About 50% of the men who served as ELAS andartes were veterans of the Albanian campaign of 1940–41, the "epic of 1940" when Greece defied the world's expectations by defeating Italy, and gave as one of their reasons for joining EAM a desire to uphold Greek national honor by continuing the fight.

In city demonstrations, we see her as a pioneer, a fighter, courageous and defying death: first in the line of battle the country girl defends her bread, her crops; but we see her even as an andartissa, wearing the crossed belt of the andartes, and fighting like a tigress".

[32] In the EAM propaganda play O Prodotis (The Traitor) by Yorgos Kotzioulos, the story line concerns an old man living in a village named Barba Zikos who argues with his son Stavos about EAM's reforms; the elder Zikos contends that equality for women will destroy the traditional Greek family while his son maintains that sexual equality will make the Greek family stronger.

[38] To address traditional concerns about "family honor", EAM had a strict rule forbidding sexual relationships outside of marriage between male and female members.

[44] The position of EAM/ELAS in occupied Greece was unique in several aspects: whereas the other two main resistance groups, the National Republican Greek League (EDES) and National and Social Liberation (EKKA), as well as the various minor groupings, were regionally active and mostly military organizations centred on the persons of their leaders, EAM was a true nation-wide mass political movement that tried to "enlist the support of all sections of the population".

[47] Although the poorer sections of society were naturally well represented, the movement included many of the pre-war elites as well: no fewer than 16 generals and over 1,500 officers of the army, thirty professors of the University of Athens and other institutions of higher education, as well as six bishops of the Church of Greece and many ordinary priests.

The exact details of what happened have been debated ever since, but Greek gendarmes opened fire on the crowd, resulting in 25 dead protesters (including a six-year-old boy) and 148 wounded.

The clash escalated into a month-long conflict between ELAS and the British and Greek governmental forces, known as the "December events" (Dekemvrianá), which resulted in a government victory.