In 1920, he was conscripted to fight in the Greek-Turkish war of 1919-1922. He was arrested in 1922 for anti-war activity but was freed with the end of the war.
From 1923 to 1925, Pouliopoulos was prominent in the war veterans' movement and was elected president of the Panhellenic Federation of Veterans in 1924.[1]
In 1924, he was a party delegate to the fifth congress of the Comintern. Later that year, he became general secretary of the KKE. On 24 August 1925, Pouliopoulos, along with 23 others, was put on trial in Athens on charges of promoting the autonomy of Macedonia and Thrace.[2] He gave a five-hour speech in his defence and the trial was adjourned. On 22 February, 1926, the trial of the "autonomists" resumed. The charges were dropped, but instead of being released, the men were exiled to Anafi, Amorgos and Folegandros islands.
Pouliopoulos was taken to Folegandros island. He was freed in 1926 with the fall of the Pangalos dictatorship. Although he resigned in September 1926 after his leadership was blamed for the poor performance of the party, he was reinstated by the Comintern.
At the party's congress in March 1927, Pouliopoulos (along with Pastias Giatsopoulos) was removed from the Central Committee. Later that year, they were formally expelled from the party after publishing and circulating the pamphlet New Beginning (Greek: Neo Ksekinima).[3] They subsequently formed an opposition group which aligned itself with the International Left Opposition. They began to publish a journal called Spartacus from December 1928 onwards. They refused to join the Archeiomarxists group which split from the KKE, regarding it as having a sectarian attitude towards the party.
When the Archeiomarxists were accepted as the representatives of the International Left Opposition in Greece, Leon Trotsky condemned Pouliopoulos' group, which was excluded from the Trotskyist movement along with the 'Fractionalists' who had just split from the Archeiomarxists led by Michel Pablo.
In 1934, the two groups joined together to set up the Organisation of Internationalist Communists of Greece (OKDE) in 1934, and for a while Pouliopoulos maintained links with other opposition groups around Landau and Molinier, opposing the movement to create a new International from 1933 onwards. However, he took the initiative in the move to unite the Greek Trotskyists in 1938 to form the Unified Organisation of Communist Internationalists of Greece (EOKDE). In September 1938, the EOKDE was present at the founding of the Fourth International in Paris.
In 1938, after going into hiding, he was eventually arrested by the Metaxas dictatorship and imprisoned in the Acronauplia, where he continued his work. In 1943, along with over a hundred other militants, he was executed by the Italian occupation forces in Nezero, near Larissa, in retaliation for the destruction by partisans of the Kournovo tunnel. There is a postwar claim that he spoke in Italian to the firing squad, exhorting them not to commit such a crime against the anti-fascist resistance and opponents of the war. When the soldiers refused to execute him, Carabinieri are said to have done so instead.