Stalinism on Trial is a history of Communism and anti-Communism in the Spanish Civil War. It uses newly available archival material to reassess Soviet intervention in Spain and reappraise the role of Premier Juan Negrín. How did the Soviet operation affect attempts to rebuild the Republican justice system that the war had shattered? How did Negrín use the courts to combat wartime espionage and treason in the era of the Soviet mass repressions? How did wartime trials communicate politics, both domestic and international? Finally, how have Cold War politics distorted our understanding of Communism in the Spanish Civil War? Stalinism on Trial traces the Republic's tribunals through revolution and war, focusing in particular on the prosecution and "show trial" of the anti-Stalin Marxist party, POUM (Partido Obrero de Unificación Marxista), in whose militia George Orwell served. This small party was thrown onto centre stage when police arrested its leadership on suspicion of espionage and its leader, Andreu Nin, disappeared while in police custody. The ensuing prosecution and dramatic courtroom trial highlighted the contradictions of Soviet intervention in Spain. It also illustrated the disastrous impact that western anti-Communism and appeasement had on Spain's war effort. The book is at once a penetrating microhistory of the POUM's prosecution and an expansive transnational history of antifascism in interwar Europe.