In September 1941, a few months after the start of the Axis Occupation of Greece, Zervas, along with other Venizelist army officers and political figures, founded the National Republican Greek League (EDES).

The goals of EDES were the fight against the conquerors of Greece, the abolition of the Greek monarchy and the establishment of a republic on social-democratic principles.

[2] The party platform of EDES talked of a "republic in a socialist form", but the British historian Mark Mazower described Zervas's socialism as "only skin deep".

[3] Notably, the platform of EDES did not mention armed resistance, and only after Zervas was bribed with 24,000 gold sovereigns from an agent of the British Special Operations Executive (SOE) did he agree to take to the mountains to wage guerrilla war.

[2] Obese and a hypochondriac, Zervas was reluctant to take up the arduous life of an andarte (guerrilla), preferring to stay in Athens.

[2] The same report mentioned that Zervas "hopes for the best but employs a crowd of useless officers, because it would disturb the peace to fire them...As an organiser, his value is NIL".

[2] A charming man, described by those who knew him as being like a "bland and easy-going company director", Zervas was primarily a political as opposed to a military leader.

[2] Another SOE agent wrote about Zervas that he was like: "the chairman of a provincial tramway company which is boosted and kept going but always has hanging over it the shadow of radical changes to the buses in the dim future.

In November 1942, the forces of EDES and those of ELAS (under the command of Aris Velouchiotis), in collaboration with a small group of British and New Zealand expert saboteurs, blew up the Gorgopotamos Bridge.

Afterward the success of Operation Harling, a team of SOE agents led by "Monty" Woodhouse arrived to train his forces and arrange for arms shipments.

[4] At the same time, Zervas warned Woodhouse of the "dark forces of Communism backed by Russia", by which he meant the rival EAM (Ethnikó Apeleftherotikó Métopo-National Liberation Front).

[9][10][8] In the final stages of the Occupation, EDES was contained strictly in the area of Epirus, having lost Aitoloakarnania, after a mini-civil war with ELAS in 1943.

During the December 1944 clashes, EDES was attacked once more by Aris Velouchiotis, and in 24 hours was obliged to leave Epirus and fled to the island of Corfu.

[11] The US and the UK opposed his appointment suspecting him of collaboration with Nazi Germany during World War II and dictatorial ambitions.