Coming from a left-wing background, during the Second World War he was a collaborator with the Nazi Third Reich, as a result of which he served a prison sentence.
Establishing links with French groups similarly opposed to decolonization, Thiriart eventually became a European nationalist, convinced of the need for a united Europe.
[3][4][5][6] Thiriart publicly disavowed fascism and called Nazism obsolete, but his movement was still accused of having a fascist basis, partly as a result of adopting as its emblem the Celtic cross, a symbol widely used in neo-fascism, and partly because in its weekly magazine Jeune Europe it advertised the activities of the allegedly neo-Nazi Hans-Ulrich Rudel, leader of the Deutsche Reichspartei.
Thiriart's views won him many enemies, on both the orthodox right and the left, this is partly due to the fact that he was highly influenced by the thinking of Francis Parker Yockey.
[9] Seeking to support radical revolutionaries in Latin America and Black Power movements in the United States, Thiriart began to develop the idea of creating Political Soldiers, and set up training camps to facilitate indoctrination.
Thiriart was later in life a supporter of a "Euro-Soviet empire which would stretch from Dublin to Vladivostok and would also need to expand to the south, since it require(s) a port on the Indian Ocean.