It was influenced by the syndicalist politics of the Industrial Workers of the World (adopting the IWW Preamble in 1925), as well as by Garveyism, Christianity, communism, and liberalism.

The ICU experienced explosive rural growth, so that by 1927 it could boast a membership of 100,000,[6] making it one of the largest trade unions ever to have taken root in Africa before the 1970s.

While its base was increasingly rural, it also managed to make inroads into urban black communities, notably in Durban on a large scale.

At times, ICU leaders promoted a radical vision of workers and tenant farmers taking over white farms.

In the late 1920s the movement took on a millenarian aspect in the rural Eastern Cape where predictions of airborne liberation by African Americans captured the imagination of thousands of people.

By the late 1920s the South African ICU faced severe repression, especially the eviction of activists from white farms and laws enabling crackdowns on key figures.

This repression was enabled by the Industrial Conciliation Act, 1924, which exempted non-whites from labor laws and refused them legal recognition as employees.