BORN in Chicago in 1922 to Lithuanian and Russian immigrants, Leon Golub (1922-2004) grew up in the shadow of WWI and the “great slump.”

His art studies were interrupted by military service in the second world war, from which he emerged to the unimaginable news of Buchenwald and Hiroshima. Whereas the dominant postwar US aesthetic ridiculed socially committed art and retreated into the inner worlds of Abstract Expressionism, Golub confronted the inhumanity of recent atrocities.

His deliberately inelegant provocations to genteel notions of art were underpinned by layered references to antiquity. After resuming his studies on a GI grant he painted monstrous hybrids and mutilated figures which emerge from roughly applied brush marks, an example being the larger than life size Colossal Torso II of 1959, whose shockingly charred and pitted flesh and truncated body evokes Hiroshima victims.

Yet the painting also refers to the fragmented colossuses of the late Roman empire, whose grandiose abuse of power Golub associated with that of 20th-century US imperialism.

The Vietnam war fully politicised him and in 1964 he became active in New York’s Artists and Writers Protest Group. Conflict became his subject and he searched for ways of making politically committed paintings relevant to modern times. Golub confronted the all-pervasive mass media’s visual language by working from published photographs and transforming these source images into unbearably emotive art by physically challenging the traditional processes and mediums of representational painting.

Working on unprimed, unevenly cut and unstretched canvases, Golub suspended the finished works loosely against the wall from grommets, so subverting the revered status of rectangularly framed paintings.

The figures in the large Gigantomachy series of the mid-1960s (top) are based on contemporary sports photographs combined with images of the antique frieze at Pergamon which depicts the mythological battle between the Giants and Olympian Gods.

The unarmed, naked combatants are depicted on a roughly stained and blotched canvas in unpleasant combinations of purplish magenta, pink and white paint which Golub partially scraped off with a meat cleaver to deepen the impact of the combatants’ flayed flesh. The savagery of his processes paralleled his subjects’ indictment of warfare.

The Napalm and Vietnam War series which followed now referred to specific events and Golub attacked his canvases with greater savagery. With large chunks cut out of them, the scorched, scarred and splotched canvases mirror the violence of the depicted US army atrocities whose vileness are conveyed by deliberately awkward drawing, compositions and morose colour.

In the 1970s and 1980s, Golub produced his greatest works. These included the Mercenaries and Interrogators series — gigantic accusatory history paintings exposing US imperialist support of the odious counter-insurgency methods by Latin American dictatorships.

Intimidating, larger than life-size armed and uniformed soldiers and police are captured in acts of torture or military bravado as they loom over us.

Based on magazine photographs of mercenaries, the men in bright blue or green and buff uniforms are painted against flat undifferentiated red oxide or maroon backgrounds, so preventing distractions from the gruesome acts.

The men leer and grin grotesquely in awkward poses, as in a film still’s arrested motion, and their macho body language and callous expressions convey the dehumanising effects of alienation.

These paintings go beyond simple accusations of individual acts of cruelty. Like Goya’s Disasters of War they portray the perpetuators of brutal acts as desensitised products of inhumane governments whose purpose is to retain power for the powerful.

In his late paintings, Golub raged against the dystopia of urban decay, the horrors of ageing and impending death in graffiti influenced works, an example being Fuck Death of 1999.

His work is not for the faint-hearted. The visceral directness of his scenes of war and torture assault our gaze. Yet their rawness of expression is contradicted by the depth of meaning which percolates from his erudite understanding of art history, mass media and politics.

The paintings are intentionally difficult to look at and defy lengthy contemplation. In discussion with the artist Martha Rosler, Golub said: “Film passes through, painting sits on the wall. I take the fact that painting isn’t moving and I make it unendurable — you can’t sit in front of it. I myself have jumped at my own paintings.” Yet they burn with an honesty and directness which resonate long after seeing them because they cut to the core of political and social injustice.

Given the massive scale of Golub’s paintings and prolific output, a larger venue would have better suited this retrospective. The Serpentine Galleries’ exhibition over-represents his late works and omits loans from major public museums. But it does give very welcome exposure to this important artist and its display of four 1980s history paintings in the rotunda do him full justice as does the imaginative and beautifully produced catalogue. Recommended.

• Leon Golub: Bite Your Tongue runs at Serpentine Galleries, Kensington Gardens, London W2 until May 17, opening times: serpentinegalleries.org. Free.