The argument in The Wretched of the Earth that most shocked its first readers, and that Sartre amplified to the point of distortion in his infamous preface, is Fanon's claim that anticolonial violence has a cathartic dimension for the colonized. It is important to state this argument precisely, because it is almost always either sanitized beyond recognition or amplified into a simple celebration of violence that Fanon does not actually endorse.
Fanon's argument runs as follows. The colonized subject has been produced by the colonial world as a psychically shattered, self-alienating, perpetually inferior being, someone who has internalized the colonizer's contempt as their own self-understanding. The colonial world is maintained by violence. The native's body is disciplined, confined, and regulated by the constant threat and periodic reality of physical force. Within this structure, the native's aggression, the aggression that the colonial situation inevitably generates, cannot be directed outward against the colonizer. It is instead directed inward: against fellow natives, expressed in intra-community violence, in the intensity of religious ecstasy, in the violence of tribal and ethnic conflict. The colonized tear each other apart because they cannot reach the colonizer.
The moment of anticolonial struggle changes this direction of aggression. The native who participates in armed struggle against the colonial power is doing something psychologically transformative: they are acting against the source of their oppression rather than against each other or themselves. The act of violence against the colonial order is, for Fanon, not primarily the most efficient military tactic but a reconstitution of the colonized as an agent, as someone who acts on the world rather than merely being acted upon. It shatters the fatalistic, self-hating passivity that the colonial world produced. It creates, in Fanon's terms, a new person: someone who has ceased to see themselves through the colonizer's eyes and begun to see themselves as a being with a claim on the world.
This is what Fanon means by catharsis: not that violence is good in itself, but that in the specific context of the colonial world, in which the colonized have been produced as psychically destroyed subjects, the act of resistance has a reconstitutive psychological function. As the Wikipedia entry notes, the political focus of the first chapter derives from Fanon's view that violence is a means of catharsis and liberation from being a colonial subject.
Sartre's preface, however, went considerably further, celebrating anticolonial violence in terms that Fanon had not used and that, as the readingfanon.blogspot.com critical response notes, actually reinforced the Manichean thinking Fanon was trying to transcend. For Sartre, the colonized killing the colonizer kills two birds with one stone: it destroys the oppressor and liberates the oppressed simultaneously. Fanon's argument is more carefully calibrated than this. He is analyzing a psychic process, not prescribing violence as a universal political program.
The pitfalls of national consciousness, the fourth chapter of The Wretched of the Earth, is, if anything, Fanon's most prophetic and his most overlooked. Having argued for the necessity of anticolonial struggle in the first chapter, he turns in the fourth to the question of what happens after independence. His answer is devastating: if the political independence of a colony is captured by a national bourgeoisie that simply takes over the administrative structure of the colonial state without transforming the economic and social relations it was designed to serve, then decolonization is not liberation. It is neo-colonialism in a new dress.
Fanon describes the pattern with the specificity of prophecy: the national bourgeoisie, educated in the colonizer's institutions and culturally identified with the colonizer's values, uses political independence to insert itself into the privileged position previously occupied by the colonial ruling class. It does not transform the economy, it inherits and administers it. It does not create new cultural forms, it mimics the colonizer's. It manages the national territory as a trading partner of its former colonizer, and it uses the newly independent state's coercive apparatus against the same poor, rural, dispossessed populations that the colonial state oppressed. The wretched of the earth remain wretched, under new management. As Wikipedia notes, Fanon points to the necessity for each generation to discover its mission and fight for it, not to inherit independence but to actively constitute it. The failure of this constitutive struggle produces the post-independence Africa that Fanon correctly predicted: corruption, ethnic conflict, elite enrichment, and the structural re-inscription of colonial dependency.