The group that founded the Greek Socialist Party was led by A. Sideris.

The party was active in trade unions, and in 1931 the leading party member Dimitris Stratis was elected General Secretary of the General Confederation of Greek Workers (G.S.E.E.).

[3] During the Second World War, the party launched the Union of People's Democracy (E.L.D.)

was a minor resistance group compared to the communist-led National Liberation Front (E.A.M.).

The Socialist Party member Professor Alexandros Svolos became appointed President in the government formed by the Greek resistance in 1944.