Its objectives were twofold; one was to capture supposed supporters of the Nationalists, who were hiding in Madrid, mostly in premises of foreign diplomatic missions; another was to enrich the scammers by robbing the victims of money and valuables.
During the outburst of revolutionary violence in the summer of 1936 numerous individuals who feared for their life sought shelter in diplomatic premises of foreign countries; their number is currently estimated at 13,000.
[4] Following a spate of articles in foreign press which agonized about atrocities in revolutionary Madrid, early next year the Republican government tried to improve its international image and started to allow evacuation of small groups from selected legations.
Both armies dug in, and some – occasionally fierce - fighting was taking place for positions named "Casa Derruida", "Trinchera de la Muerte" and "Vértice Basurero" until the summer of 1937.
Some time in September 1937 he arrived at an idea of luring individuals who sought refuge in Madrid diplomatic missions into a trap, and obtained approval from the commander of the Brigade, Justo López de la Fuente.
[13] Taking advantage of his network of informers and collaborators Duran floated rumors about corrupted Republican militiamen ready to escort people to an underground tunnel, reportedly running across Usera to the Nationalist-held territory.
Duran also posed as a right-winger himself; since September he visited premises suspected of having been frequented by Nationalist supporters, and offered safe passage to the alleged tunnel in return for money or valuables.
Most were kept in the dungeons for a few days, some for few weeks;[18] during this period they were forced – by means of intimidation, beating and torture - to write letters which declared they were well and safe in the Nationalist zone, and/or to provide information on other right-wingers hiding in Madrid.
On basis of exhumations carried out in 1939 the Francoist authorities established the number of victims as at least 67 (65 males and 2 females), though some 30 more dismembered or highly decomposed corpses found in the area were also tentatively attributed to the Usera scam.
Exhumations led to discovery of the mass grave and single corpses in basements of some buildings; in October 1939 forensic experts from Escuela de Medicina Legal of Universidad Central completed a 26-page report with all 67 remnants found described in detail.
[23] In 1944 36 positively identified corpses were again exhumed and laid to rest in a basement mausoleum within a newly built religious compound in Usera,[24] where they remain until today.
In For Whom the Bell Tolls, published in 1940, the key protagonist Robert Jordan, a SIM operative, recollects having shot two unarmed fascists, captured in Usera.
[30] In his famous novel Hemingway made also numerous references (unrelated to Usera) to Gustavo Duran Martínez, a real-life commander of the Madrid SIM between August and October 1937.
In a 1961 letter to Hugh Thomas, the author of freshly published history of the Spanish civil war, Duran protested the paragraph which referred the Usera scam and declared it based on faked Causa General documents; this intervention added to confusion.
[32] Apart from the extensive Causa General documentation, the Usera scam has been treated in few articles in popular periodicals,[33] has been dedicated a text published by Fundación Nacional Francisco Franco[34] and features in detail on some private websites.
[36] Others go further and advance doubts; following earlier Duran's skepticism they note that the only source available is the post-war Causa General; they underline that the Francoist investigation can not be trusted as it was biased and it failed to produce conclusive evidence.
In numerous historiographic works,[38] including these which specifically discuss Madrid during the war,[39] the Usera scam is referred with no reservations; this is also the case of some academic projects.
Websites or articles dedicated to history[43] or tourism[44] in Usera, which is now a densely built residential district of Madrid known for its Chinese minority, do not mention the tunnel episode.
Religious service has been held for souls of the deceased every some time and victims of the Usera scam are commemorated also during some general events, intended as part of "la otra memoria".