The International Brigades numbered some 35,000 fighters – most were volunteers, many were communists – from around eighty countries. They were a unique phenomenon at a historic moment: the Spanish Civil War, as a ‘dry run’ for the larger conflagration soon to engulf Europe and the world, was the first major attempt to defend democracy from emergent fascism, the first conflict to feature photographers as part of the unfolding narrative of war, the first to feature large-scale bombing of civilian populations, and the first war to include, at least initially, a significant number of female fighters.

On the surface, the story is simple: twenty years after World War I, a new generation of idealists from around the world converged on Spain in order to take up arms – any arms as it happened, no matter how faulty – against a military coup that sought to overthrow the Second Spanish Republic (1931–39). The great majority of Brigaders had never been out of their home countries before; even fewer had ever seen Spain or any Mediterranean country. Many had never fired a weapon. From their first engagements in the defence of Madrid to the Battle of the Ebro in 1938, by which time the war was lost, they showed enormous bravery and political commitment. As in any war, however, there was a darker side. While he is obviously sympathetic, Tremlett is too thorough an observer to fall into simple hagiography. There was much that was not glamorous but rather cruel, inhumane, or simply illegal. At one point in the siege of Madrid, a group of Brigaders debated whether to shoot an enemy Moroccan soldier who had become lost. One of them objected that the soldier was ‘only a man, a victim of colonialism’. Tremlett is deadpan: ‘They killed him anyway.’ There were summary executions, rapes, and war crimes; while many Brigaders would later play significant roles as resistance fighters against fascism during World War II, others would go on to serve deeply undemocratic regimes, most especially in Eastern Europe.

History has looked kindly, if ruefully, on the International Brigades. The cultural narrative, aided by legions of writers, poets, and artists – international participants and Spaniards in exile – has lauded this first great international co-operative fight against fascism. Its tragic fate as the one place young allies failed to stop fascism in its tracks has only added to its aura. For the international left, Republican Spain was for decades the great ‘what might have been’ of the twentieth century.

Tremlett’s account adds nuance and humanity to such simplifications. Across fifty-two short but compelling chapters, each one focusing on a particular place, month and battle, we meet an array of idealistic young fighters and their Babel of commanders: some skilled and determined, others confused, frightened, and largely hopeless. Tremlett examines troves of personal correspondence and diaries to illustrate the human side of the international effort in Spain, packing his book with previously unknown characters and anecdotes. It is as if familiar black-and-white newsreels suddenly sprang to colourised life. From these otherwise anonymous persons come ecstasies and tribulations, from the thrill of revolution to the stinking horror of war. We find a young Simone Weil joining the Durruti Column, only to be relegated to cooking duties and sent home after badly burning herself with olive oil, shocked by the casual murder of priests and teenage ‘fascists’. She was far from the only one to learn the sudden and pitiless brutalities of war.

Elsewhere, famous names lose their sheen. Some, not surprisingly, considered Hemingway both a ‘tourist’ and a ‘prick’: his takes on the Spanish conflict, including the often absurd For Whom the Bell Tolls (1940), have not aged well. He was arrogant and misogynistic in general, specifically in his attitude to the photographer Gerda Taro. Taro, herself constructed over recent decades as something of a feminist hero, was not always a role model, being complicit, along with Robert Capa, in the occasional staging of fake photos. This matters: the photographs of Capa and Taro helped to lay the visual groundwork for the romanticised narrative that was to grow over subsequent decades.

At the risk of being parochial, and small though the Australian presence was, one laments the almost complete lack of Australian voices in this book. Particularly missed is Lloyd Edmonds, an ambulance and truck driver based in Albacete and active on the Teruel front, whose Letters from Spain (1985), edited by the late Amirah Inglis, is a neglected classic of Australian writing.

The rest, of course, is history: defeat, pain, withdrawal. Again and again we meet enthusiastic young men and women with bright futures, only to see them killed – often in extreme and senseless violence – within a few pages. While the precise number will never be ascertained, at least 7,000 volunteers from across the world died in Spain. Many of their bodies have never been recovered. Thankfully, some breathe again here through their letters and diaries, their fears and desires rescued from forgotten archives to be woven into this brilliant tapestry of human folly and ambition.