Revolutionary Marxism in Spain, 1930-1937 examines the impact of Trotsky’s political thought upon those Spanish communists who dissented from the ‘general line’ laid down by Moscow. It explores the political ideas of leading POUM figures, Andreu Nin and Joaquín Maurín, and their complex relationship with Trotsky. The contention is that the POUM owed far more to Trotsky than many of the party’s historians care to admit. Drawing heavily upon Spanish sources, the book seeks to present and explain the POUM’s political ideas in order to understand why the party adopted the positions it did. The author engages with broader scholarly debates around the role of the POUM in the Spanish Civil War and Revolution, especially those surrounding the Popular Front.