From the moment it began in 1936, the Spanish Civil War became the political question of the age. Hitler and Mussolini quickly sent aircraft, troops and supplies to the right-wing generals bent on overthrowing Spain’s elected government. Millions of people around the world felt passionately that rapidly advancing fascism must be halted in Spain; if not there, where? More than 35,000 volunteers from dozens of other countries went to help defend the Spanish Republic. Adam Hochschild, the acclaimed author of King Leopold’s Ghost, evokes this tumultuous period mainly through the lives of Americans involved in the war.