This evocative study is the first comprehensive history in English of all the 35,000 international volunteers who fought the combined forces of Hitler, Mussolini and Franco in Spain in the war of 1936–9. Far more than a civil war, it was Europe’s war against fascism. Giles Tremlett encapsulates its huge stakes perfectly in his opening sketch of the preparations for Barcelona’s People’s Olympiad, which was to have been held in July 1936 as a protest against the official Olympic Games in Hitler’s Berlin but was aborted following the eruption of civil war. The Olympiad’s organisers took a radical stand against contemporary prejudices, specifically requesting the inclusion of black athletes in the US team after none were included in the original selection. Later, it was in the US contingent of the International Brigades, the Abraham Lincoln Battalion, that the first ever racially integrated American fighting force was born, commanded for a time by a black officer (by contrast, the US army remained segregated throughout the Second World War). The young American poet Muriel Rukeyser, who went to Spain to report on the Olympiad and whose own life was marked forever by her experience there, wrote that she ‘saw the future stand up/free and alive’.

But that future was not a certainty. Tremlett underscores how fear for the future was what anchored the anti-fascism of so many international volunteers, whether soldiers or medical support staff (hundreds served as doctors, nurses and ambulance drivers).