Like so many women artists of her generation, Nancy Spero was overlooked for too long. During the early part of her long and defiantly uninhibited career the male-dominated art world preferred to ignore Spero’s achievements. But she never felt disheartened by this neglect. On the contrary: her finest work always sprang from a stubborn, angry refusal to be defeated. The female figures who energise her art are fuelled by a militant dynamism as they run, fly and fight through a succession of dramatic encounters.

As she grew older, and international attention began at last to focus on her work, Spero grew even more determined to make epic art from the battle against oppression of so many kinds. Her scrolls and printed installations became ever more monumental. With immense panache, she deployed them in spaces where every surface, floors,ceilings and walls, sprang into highly charged activity. Nothing, it seemed, could prevent her intense protagonists from combating and even humiliating the forces ranged against them.

Spero was born in 1926 in Cleveland, Ohio, and her family moved to Chicago when she was a year old. While studying there at the School of the Art Institute, she met a similarly defiant young figurative painter, Leon Golub. A war veteran, he remained preoccupied by global conflict until his death in 2004, by when he had been married to Spero for 53 years. And when they began living together, Golub and Spero were united by their opposition to a US art world obsessed with avant-garde abstraction.

Hence their youthful decision to leave the US in 1956 and to explore Europe. Spero was excited above all by Ancient Etruscan art when they visited Italy. But in Paris, where they settled in 1959, she found supreme stimulus in the work of Antonin Artaud, whose manic-depressive art and writings culminated in the Theatre of Cruelty.

Spero, who had briefly studied at the Ecole des Beaux-Arts in Paris a decade earlier, warmed to the unbuttoned vehemence of Artaud’s work. She identified with his profound sense of alienation, and felt liberated by the idea of launching a spirited attack on everything she loathed in the postwar world. Dark paintings inhabited only by indistinct figures, all embroiled in strangely erotic conflicts, dominated her output in the Paris years. She learnt how to give vent to a sense of primal indignation and rage, and entitled one especially provocative 1960s image Les Anges, Merde, Fuck You.

Artaud’s unfettered influence grew even more arresting after Spero and Golub moved back to New York. The Vietnam War intensified her vision, prompting her to include destructive helicopters and bombers in two outstanding series of works: the Artaud paintings and the Codex Artaud. Prehistoric deities and dildo dancers were united, in these outspoken images, with female warriors driven by a crusading urge to oppose the ever-menacing forces of annihilation.

At one point in the series Spero included these revealing words: “Artaud I couldn’t have borne to know you alive your despair.” While acknowledging his crucial influence, she also implied here that she used him as a springboard for her own, independent exploration of the nightmare of US involvement in Vietnam.

“In some of these paintings,” Spero said, “the image of the helicopter has breasts hanging down and people are hanging on with their teeth, like a circus act.”

Grotesque humour informs her work as well. And although Vietnam aroused Spero’s ire, she set no limits on disparate sources that nourished her work. Like a theatre director, she treated these figures as a cast of characters in a drama of her own making. More like a nightmare than a play, the outcome conveyed her disgust and horror at the slaughter of civilians across Vietnam. Nor did her War Series (1966-70) lose its relevance in later decades. When displayed at the Lelong Gallery in New York in 2003, its macabre vision still seemed to apply with unnerving power to the forces of destruction assailing society in the emergent 21st century.

While working on all these protest pieces Spero became involved with the women’s movement as well. After supporting the Art Workers Coalition, she decided in 1969 to join the splinter group Women Artists in Revolution (WAR). True to its name, the group staged protests against racist and sexist policies in New York City museums. During the 1970s the dominance of white male artists was challenged with ever-gathering resolve in North America and Europe alike.

Spero’s work became overtly feminist, and in 1977 it burst upon Britain when the London-based Studio International magazine published a special issue called “Women’s Art”. The leading US critic Lucy R. Lippard, invited to contribute to this issue, included Spero among five “political artists” who were each given a double-page spread. “Torture of Women” was the title uniting Spero’s collage panels. One of them highlighted an atrocity in Chile, where General Pinochet had presided over appalling and incessant suppression since 1973. Spero concentrated on the plight of a 29-year-old model called Marta Neira, who was arrested by Chile’s “brutal secret police” and sent to prison where “her nose was broken and she had welts all over her. She had been subjected to electric shock and to sexual abuse.”

The other panels in Spero’s Studio International contribution widened this theme to include gouaches of battered, screaming yet resilient women from distant eras. “Torture today is essentially a state activity,” she wrote with her typewriter on one image, but Lippard pointed out in an accompanying essay that “Spero’s scrolls and panels weave public and private violence, the harshness of her content visually arguing with subtleties of her execution”.

In 1980 Lippard curated a highly polemical show at the ICA, London, called Issues. Assembling an international selection of socio-political work by women artists, it included Spero’s denunciation of torture with giant hand-printed lettering and anguished painted figures. During the 1980s her fiercely committed and ever more inventive art gained widespread recognition at last. In 1988 she was given a solo show at the Museum of Contemporary Art in Los Angeles. And then, four years later, an exhibition at the Museum of Modern Art in New York.

Spero made a spectacular impact in England, too. When the Ikon Gallery, Birmingham, reopened in new premises in 1998, she made a large installation for the lofty upper room. It unleashed a cavalcade of super-charged women all over this luminous white space, where they flew, gyrated and hurtled with emancipated glee.

“Let the priests tremble,” exclaimed the crimson words on the walls, before yelling: “Too bad for them if they fall apart, on discovering that women aren’t men.”

Ranging from cave paintings and Celtic carvings to contemporary photos of Hollywood movie stars, Spero brought past and present into a surprising, witty and audacious new unity.

Although plagued with arthritis in her final years, she produced an ambitious mosaic installation for a Manhattan subway station at the Lincoln Center in 2001. Three years later Golub died. But she kept the partition that had long divided his studio from hers in their Greenwich Village loft. His loss did not prevent her, as late as 2007, from reaffirming a fundamental commitment at the Venice Biennale. In the Italian Pavilion, visitors were confronted at once by her Maypole/Take No Prisoners, and she declared with characteristic verve that it was “all about victimage”.

Nancy Spero, artist, was born on August 24, 1926. She died on October 18, 2009, aged 83