Siege of Cuartel de la Montaña The Siege of Cuartel de la Montaña was the two - day siege of the military barracks which marked the failure of the uprising against the Second Spanish Republic in Madrid , Spain on 18 – 20 July 1936 , at the start of the Spanish Civil War . The bulk of the security forces in Madrid remained loyal to the government , and supported by workers ' militias , crushed the uprising . Background . Political . On July 17 – 18 a part of the Spanish army , led by a group of officers ( among them Generals Jose Sanjurjo , Francisco Franco , Emilio Mola , Manuel Goded and Gonzalo Queipo de Llano ) , tried to overthrow the Popular Front Government of the Second Spanish Republic . The occupation of the capital , Madrid , was one of the prime goals of the Spanish " coup " of July 1936 . However the " coup " in this particular location was ill - planned and clumsily executed . There was no coordination between the diverse elements who were hostile to the Republic ( the falangists , the army officers around Fanjul , and the members of the " UME " ) ; the coordinator of the plot in Madrid , Colonel Galarza had been detained and General Villegas , the elderly and indecisive appointed leader of the rising in Madrid decided at the last minute to avoid direct participation . General Joaquín Fanjul replaced him at short notice . There was a particularly strong concentration of pro - government forces in Madrid . These included para - military security forces and organized ( though at this stage generally unarmed ) union groups . Finally , a large portion of the officers and soldiers of the regular Madrid army garrison were uninvolved in the plot and pre - disposed to remain loyal to the elected government . Montaña Barracks and Madrid garrisons . Located near the former Royal Palace of Madrid to the west of the central city , the Montaña Barracks , built in 1860 , was comprised three separate buildings joined together to make up a large fortress - like structure fronted by a wide glacis and parapets It was normally garrisoned by three regiments of infantry , a regiment of engineers and specialist units , although in July , 1936 , many of the soldiers were on summer leave . A further eight regiments plus four independent battalions and two artillery groups were based in other garrisons located in and around the city . Finally , 25 companies of Assault Guards and 14 of Civil Guards were either located in Madrid or had been brought in by the Republican authorities shortly before the July rising . The role of these trained security forces was to prove crucial . The coup in Madrid . July 18 . On July 18 news of the military rising in Morocco reached Madrid and the " UGT " and " CNT " demanded the distribution of arms . However the government initially refused to give weapons to civilians . Nevertheless , a group of young officers led by Lt . Colonel Rodrigo Gil , distributed 5 , 000 rifles among the workers . The plotters had planned that General García Herrán would seize the Army camp at Carabanchel and General Fanjul would occupy the inner city from the Montaña Barracks , located in " Principe Pio " , close to the " Plaza de España " . Other rebel officers should then seize the Getafe base and the air base of " Cuatro Vientos " , but the plan failed . Furthermore , the commander of the Civil Guard in Madrid , General Pozas and the Assault Guard ( around 6 , 000 men ) remained loyal to the government . July 19 . On July 19 , the new government of Prime Minister Giral decided to issue weapons to the unions . 65 , 000 rifles were handed over , but only 5 , 000 had bolts and the other 60 , 000 bolts were stored separately in the Montaña Barracks . The commander of the barracks , Colonel Francisco Serra , disregarded the order of the Minister of War to hand over this essential equipment , effectively marking the beginning of the uprising in Madrid . On the morning of July 19 , General Fanjul arrived at the Montaña Barracks , as did groups of officers from the other Madrid garrisons and a number of falangist and monarchist volunteers . After lecturing his fellow officers on the political goals of the military rising , Fanjul tried to advance into the city streets with his troops ( now numbering 2 , 000 officers and soldiers plus 500 volunteers ) . towards the city center , but a crowd of about 8 , 000 , organized by the " CNT " and the " UGT " , some armed , had gathered around the barracks . Assault Guards were seen taking up firing positions on the roofs of neighboring buildings . Fanjul decided to withdraw into the barracks complex and await help from the other garrisons of the city , rather than attempt to break through the siege . Nevertheless , the coup had failed in the other city garrisons . In Carabanchel , General García Herrán had been killed by his own troops while trying to raise them against the government and the artillery barracks there had been secured by loyalist officers . The engineer units at El Pardo had been withdrawn to the north by their officers under the pretext of suppressing risings elsewhere in Spain . The No . 1 Infantry Regiment at Retiro had surrendered their barracks to government forces without opposition . Finally at the Getafe air - base , rebels had been defeated by loyal troops after the death of an air force officer . This permitted flights to be made over the Montaña Barracks the next day , initially to drop leaflets and then bombs . July 20 . On the morning of July 20 , two 75 mm guns commanded by a retired artillery officer Captain Orad de la Torre , plus one 155 mm gun joined the siege . Also , a Breguet XIX warplane from the " Cuatro Vientos " air base bombed the barracks . At half past ten , one bomb wounded Fanjul and Sierra . A few moments later some soldiers inside the barracks waved a white sheet from the windows apparently with the intention of surrendering . Against the orders of Lieutenant Moreno of the Assault Guards , who were leading the attack , the crowd ran forward but other defenders fired at them from the barracks with machine guns . This happened twice , killing or wounding numbers of people . Around noon , the crowd maddened by these incidents broke through the main gate . Some surrendering defenders were massacred by the crowd in the main courtyard , several being thrown from an upper gallery . Photographs show the courtyard littered with bodies . Captain Orad de la Torre and Arturo Barea both reported seeing a number of rebel officers who had gathered in a mess room and then shot themselves . At least some of the Falangist and monarchist volunteers wearing civilian clothes were able to slip away in the confusion . Colonel Serra was among those killed immediately after the fall of the barracks . The wounded General Fanjul together with other surviving rebel officers , was detained in Madrid ' s Model Prison for trial . Of the 145 rebel officers who had been in the Cuartel de la Montaña , ninety - eight died in the fighting , were killed after surrender , committed suicide or were subsequently executed . Total losses among the defenders are estimated at about 200 dead while the casualties among the attacking forces appear to have been significantly lighter . The rifle bolts and ammunition that had been the immediate cause of the attack on the barracks were seized by Assault Guards and taken to the Ministry of War . Aftermath . After having defeated the rebel troops in Madrid , columns of militia , civil guards and assault guards left Madrid and occupied Alcala de Henares and Guadalajara . Later Fanjul and Villegas were convicted and executed for military rebellion . The damaged barracks remained in ruinous condition until it was demolished and the area added to the public gardens of the Calle de Ferraz .