When civil war broke out in Spain in 1936, tens of thousands of young men and women from across the world flocked there to fight against the Nationalist uprising. Though their history has been told before, Giles Tremlett’s The International Brigades: Fascism, Freedom and the Spanish Civil War (Bloomsbury, 2021) draws upon previously unavailable materials to tell the stories of the war they fought. Though these people came from a variety of backgrounds and held a range of different left-wing political views, what united them was their opposition to fascism. Despite their disorganization and lack of training, they made an impact on the battlefield soon after their deployment, and became a highly visible presence in the war against Francisco Franco’s Nationalist forces. While the Spanish Republic they fought for was ultimately defeated, Tremlett explains how many of those who served in the Brigades continued their struggle against fascism during the Second World War, reflecting the lasting legacy of their service for their cause.