‘Me, I am going to Spain with the boys,’ Martha Gellhorn famously told a friend in 1937 as she boarded a ship sailing from New York to France. ‘I don’t know who the boys are, but I am going with them.’ She knew perfectly well with whom she was going: Ernest Hemingway, who was on the point of abandoning his second wife for her. They were off to cover the Spanish Civil War, where Franco’s Nationalists were making steady gains against the army of the legitimate republic. But it is the women, not the boys, about whom Sarah Watling writes here: the reporters, photographers and authors for whom the Spanish conflict became, in the later words of the American novelist Josephine Herbst, the most important event ‘in the life of the world’, a ghastly, menacing foreshadowing of the war to come.

Along with Herbst, fresh from writing about Batista in Cuba, and Gellhorn, now twenty-eight and the author of a much-praised book about the Depression, The Trouble I’ve Seen, there was Nancy Cunard, the daughter of an American heiress and an English peer; thin-lipped, with a small head, cropped hair and outlandish clothes, she went to Spain as correspondent for the Associated Negro Press. There were also a 22-year-old black American nurse, Salaria Kea, who had been working in a hospital in Harlem and fighting her own battles with racism; the bestselling novelist Sylvia Townsend Warner, ‘quick, dark and lean; bespectacled and frizzy of hair’, a lesbian and a communist with a ‘flair for heckling’, who travelled with her partner, Valentine; and Nan Green, who had run a second-hand bookshop in the Caledonian Market in London and whose husband was serving as an ambulance driver. And, in this war in which the picture was as important as the word, with magazines on both sides of the Atlantic giving considerable space to illustrations, there was the tiny – barely five foot – photographer Gerda Taro, who looked like a boy and had red-blonde hair. Taro, who had spent time in a prison in Leipzig for distributing anti-Nazi leaflets, travelled to Spain as the companion of the more famous Robert Capa. All of them, Watling writes, ‘saw history coming and went out to meet it’.

What drew Watling to these women was that they chose not to be dispassionate but to take sides, rejecting what Gellhorn dismissed as ‘all this objectivity shit’ in their support for the Republicans. Only Virginia Cowles, a secondary character here, whose book Looking for Trouble is one of the best memoirs of war reporting ever written, tried to cover both sides, which made her universally suspect. The rest of them filed stories and pictures about horrors and atrocities perpetrated by the Nationalists, of which there were many, and turned a blind eye to the cruelty of the Republicans, whose deep divisions (and many acronyms) left them confused. All extolled participation, along with the need to take note of and not run from what was happening in Spain.

In 1937, Cunard, who believed passionately in the power of the arts, sent a message to over two hundred well-known writers with a question: were they for or against the legal Republican government of Spain? Their answers, published as a pamphlet, Authors Take Sides on the Spanish War, were as positive as she had expected: only five of the 148 whose responses were printed declared themselves against it. ‘Every man to his battle,’ she wrote. ‘This is yours.’

Another of Watling’s characters is Virginia Woolf, not long back from driving with her pet marmoset through Germany, where she had become caught up in a deeply alarming rally welcoming Hermann Göring. Woolf did not go to Spain but thought about it obsessively. She filled her notebooks with clippings relating to the war, while mourning her nephew Julian Bell, killed driving an ambulance for the Republicans, and railing against the brutal, masculine culture that had nurtured war.

The women Watling has chosen to describe were brave. They made heroic efforts to get themselves to the front and sent back anguished reports of refugees strafed by Nazi bombers, small children killed as they played in the streets and liberated prisons where they had discovered evidence of torture. Herbst had trouble finding a niche for herself among the cliquish foreign reporters who gathered around Hemingway in the Hotel Florida in Madrid, where celebrities were revered and animosities simmered. When she finally reached the front line she found the earth often ‘streaked with the slime of dead things’. The intrepid, reckless Taro was killed when a tank collided with the car to which she was clinging. She was a remarkable photographer, though her true talent did not come to light until the 1990s, when a cache of her negatives was discovered.

Group biographies are notoriously hard to write. But Watling knits together with considerable skill the details of her characters’ lives and adventures in Spain, bringing them alongside each other in set pieces, then following them individually as they move through the war, file their stories, leave and return. She also intersperses her narrative with perceptive commentary. Each of these women, as she shows, battled with her own demons. Gellhorn fretted about getting old and not being able to write; Nan Green struggled with the loss of her husband, killed on the last day of the war; the extraordinary Cunard constantly feared that she might not be able to ‘tell the truth’ and wondered how to raise money for the defeated Republicans, many of whom crossed over the border into an unwelcoming France and later died in concentration camps.

Each of these women, too, in her own way, was sustained by a desire, in the words of Gellhorn, to make ‘an angry sound against injustice’. As Josephine Herbst would write, with wry hindsight, ‘People cared. It was a decade when people believed in the possibility of their own powers.’