1936 it was made public that all policing formations - Guardia de Asalto, GNR, CIV, MVR, IGM – would merge in a new service, Cuerpo de Seguridad (CS). Of its two branches, Grupo Uniformado and Grupo Civil, the latter included Sección de Investigaciones Especiales; this plain clothes investigation service became the backbone of policing structures managed by the Ministry of Interior. However, the same minister in June 1937 carved out from DSG a unit named Departamento Especial de Información de Estado (DEDIDE), basically a counter-intelligence agency, which also in Madrid ran its own network of operatives and premises. Two months later, in August 1937, the Ministry of War declared setting up a new organization, supposed to gather all espionage, counter-espionage and information activities: Servicio de Investigación Militar (SIM). From that moment onwards SIM became the key state instrument in fighting presumed conspiracy. In March 1938 it incorporated the dissolved DEDIDE. The army intelligence units like Section Two of the General Staff, later known as Servicio de Información del Estado Mayor (SIEM), continued to operate independently, yet except late 1936/early 1937, when military counter-espionage Special Services remained fairly active, they did not contribute to public order system in Madrid. Modus operandi Units forming the Republican realm of public order relied on various methods in their pursuit of suspects. The most popular one was response to tips and denunciations, either from individuals co-operating with the security, most prominently porters of the UGT union of porters, or madrileños who were not related to the policing network. Another method was the systematic search, usually based on files held by prewar offices like police departments, or papers obtained from raiding premises of right-wing parties or institutions. One more method was street vigilance and monitoring, related to key objects or the black market. Finally, certain units specialized in setting up traps, like the false embassy of Siam or the so-called Túnel de Usera. Some individuals were apprehended and executed on the spot or shortly afterwards, at times maltreated before death. Many of them, however, ended up in some sort of incarceration; it might have been in official prison compounds, in arrests on police stations or in detention centers operated by various groups, usually in former convents or other suitable large buildings. It seems that incarceration usually lasted no longer than few months, but there were cases of much longer detention. An interrogation followed; depending upon the