Encountering organized antisemitism from the Greyshirts and those celebrating the centenary of the Great Trek, he moved towards Marxism,[2] joining the Fourth International Organisation of South Africa (FIOSA).
From 1944 to 1946, Hirson was full-time-organiser for the Workers' International League, a short-lived Trotskyist group, trying to develop black trade unions despite the Suppression of Communism Act.
After the Sharpeville Massacre Hirson felt discouraged by the political failure to combat apartheid and in 1960 he wrote a critique of the movement, called 10 Years of the Stay at Home.
[2] In the early 1960s, Hirson organized a National Committee for Liberation, later known as the African Resistance Movement (ARM), with other Trotskyists and younger members of the ANC.
He died in London in 1999, aged 77, from the cumulative effects of a long-term degenerative paralysis of the bone structure, one of several health problems exacerbated by his imprisonment.