A Checa in Spain (named after the early Soviet secret police units) relates to any one of several unofficial or clandestine paramilitary police deployed during the Spanish Revolution of 1936 in Republican zones to detain, interrogate, torture, extrajudicially condemn and subsequently mutilate or murder those suspected or accused of sympathizing with any supposed enemy, whether genuine opponents or not.
The historian Peter H. Wyden, in his work The Passionate War, The Narrative History of the Spanish Civil War 1936–39 describes the Checas in the following way:
The investigative bodies created by left-wing political parties and unions in the large cities of the republican rearguard when the military pronouncement of July 1936 failed, have historically been called Checas. The name came from the first Soviet political police. created in Russia in 1917. CHEKA is the Russian acronym for All-Russian Extraordinary Commission for the Suppression of Counterrevolution and Sabotage, precursor of the OGPV, NKVD and KGB[1]