What became known as the Spanish Civil War began on 17 July 1936 when a group of right-wing generals staged a military coup, aimed at overthrowing Spain's democratically elected government. The coup was supported by military units in many cities around Spain. However, some of the country's biggest cities, such as Madrid, Barcelona and Bilbao, remained under government control.
Within days of the coup, Hitler and Mussolini intervened on the side of the insurgent generals. The Soviet Union came to the aid of the Loyalists, also known as the Republican forces. Britain, France and the US decided to remain neutral, even imposing – and enforcing – an embargo on the sale of arms to the Republic.
The battle for control of Spain turned into a horrific conflagration that lasted almost three years. The new medium of photojournalism brought horrifying images of the conflict into homes around the world. In an unprecedented display of international solidarity, some 35,000 volunteers from 50 nations joined the International Brigades and risked life and limb to defend the Republic.
From their strongholds in the south and west, the Nationalists – supported by Italian and Moroccan troops – advanced northwards, capturing cities from Republicans weakened by the embargo. Barcelona and the rest of Catalonia fell in early 1939, and Franco's troops marched into Madrid in April.
1936: People run to the nearest shelterUnknown artistCirca 1936: Nationalist troops shelter behind a wall on the Sierra de Guadarrama front, while they engage government troops during the advance on MadridKeystone/Getty ImagesCirca 1936: Republicans fight on a street of an unidentified town against Nationalist forcesAFPCirca 1936: General Franco, Chief of Staff Barroso and Commander Carmenlo Medrano look at a mapAFPCirca 1936: A young Republican marches in a street of an unidentified villageAFPCirca 1936: Female snipers, fighting for the government forces, are pictured in action during the Spanish Civil WarKeystone/Getty ImagesCirca 1936: Scenes of destruction along the roads at the height of the Spanish Civil WarThree Lions/Getty ImagesCirca 1936: Refugees walk up a mountainside. Many thousands of Spanish families crossed the Pyrenees to reach FranceKeystone/Getty ImagesCirca 1936: Refugees from the Spanish Civil War pack the roads to Perpignan in France. They were dispatched to rudimentary internment campsThree Lions/Getty Images5 August 1936: Spanish Civil War refugees arrive in GibraltarDerek Berwin/Fox Photos/Getty Images10 August 1936: Residents of Gibraltar and Spanish refugees watch the bombardment of AlgecirasFox Photos/Getty Images6 September 1936: A Republican farmer defends a farm on the outskirts of the Basque city of Irun against Nationalist forces. A comrade lies dead by his sideKeystone/Hulton Archive/Getty Images6 September 1936: Journalist Raymond Walker risks his life by dashing across the International bridge from Hendaye in France, to Irun in Spain, under a hail of bullets, to save a babyHorace Abrahams/Getty Images8 September 1936: Republican militia men search through the wreckage of their barracks in Madrid after it was bombedFox Photos/Getty Images13 September 1936: Pro-Nationalist residents and troops celebrate on the streets following the capture of Donostia-San SebastiánFondo Marín. Pascual Marín; Kutxa_Fototeka28 September 1936: A mass is celebrated at the Alcazar in Toledo after the arrival of Nationalist troops that ended a 70-day siege by Republican forcesAFP7 November 1936: Nationalist troops escort captured Republican soldiers on the Samosierra frontKeystone/Getty Images9 November 1936: Moorish troops fighting with the anti-Communist forces rest after a victorious encounter in a suburb of MadridKeystone/Hulton Archive/Getty ImagesPro-Republic Basque fighters are seen in the town of Elgeta in the Basque Country, around 1936-1937Public domain13 November 1936: Citizens of Irun give the fascist salute during a parade after the city was taken over by the Nationalist troopsMaeers/Fox Photos/Getty Images13 November 1936: Boys and girls give the fascist salute in Irun after the city was captured by the NationalistsMaeers/Fox Photos/Getty Images13 November 1936: Young boys with dummy rifles over their shoulders march in the streets of Irun in a parade organised by the Nationalists after they conquered the cityMaeers/Fox Photos/Getty Images11 February 1937: Republican forces lie in ambush in a village near MadridHulton Archive/Getty Images2 April 1937: Nationalist troops loyal to General Franco advance, bayonets fixed, through the debris of houses at Madrid wrecked in air raidsHulton Archive/Getty ImagesCirca 1937: Republican soldiers carry a dead comrade at the Navacerrada Pass. This photo was taken by Gerda Taro, regarded as the first female photojournalist to cover the front lines of a war – and to die while doing soGerda TaroThe town of Guernica, after it was bombed by German and Italian aircraft on 26 April 1937, killing between 150 and 1,650 civiliansUniversal History Archive/UIG via Getty Images25 May 1937: Some 4,200 Basque children arrive at Southampton aboard a liner, having been rescued from the horrors of the Spanish Civil WarE. Dean/Topical Press Agency/Getty ImagesCirca 1937: Reporters mingle at the front line with Republican troops. Ernest Hemingway can be seen (in glasses) in the backgroundLondon Express/Getty ImagesCirca 1937: Nationalist soldiers give the fascist saluteKeystone/Getty ImagesCirca 1937: Bodies lie on a street after a sudden air raidCentral Press/Getty Images13 November 1937: Bodies of children await burial after a Nationalist air raid on their school in BarcelonaKeystone/Getty ImagesCirca 1938: Part of the city of Santander, which was severely damaged during fightingThree Lions/Getty ImagesCirca 1938: A member of the French frontier troops helps a family of refugees cross the border from SpainKeystone/Getty Images24 November 1938: General Francisco Franco salutes during the singing of the Nationalist anthem at Burgos Cathedral25 November 1938: Soldiers camouflage a car during the Spanish Civil WarHulton Archive/Getty Images1939: Nationalist troops enter Barcelona in Carro Veloce CV33 tankettes, made in ItalyKeystone/Getty ImagesJanuary 1939: Nationalists in Barcelona rejoice at the arrival of General Franco's forces in the city. Barcelona was the last major Republican stronghold to fall to the NationalistsKeystone/Getty Images30 January 1939: General Yagüe marches victoriously through Barcelona, four days after his troops had taken control of the cityAFP29 January 1939: A woman waits with her few remaining possessions at the French border at Perthus, after the authorities opened the borders to refugees from the Spanish Civil War, shortly after the fall of BarcelonaFox Photos/Getty Images1939: Refugee families walk to safety during the Spanish Civil WarKeystone/Getty ImagesFebruary 1939: Two members of a rescue party assist an elderly woman fleeing the Spanish Civil WarTopical Press Agency/Getty ImagesCirca 1939: Young refugees from the Spanish Civil War rest on the French borderLondon Express/Getty Images8 February 1939: Refugees are watched over by soldiers at an internment camp in Le Perthus, France, on the border with SpainKeystone/Getty ImagesCirca 1939: A dead horse, a casualty of the Spanish Civil WarEvans/Three Lions/Getty Images28 March 1939: Nationalist troops enter Madrid and are welcomed by the populationHeinrich Hoffmann/ullstein bild via Getty Images1 April 1939: A family searches through the rubble where their home in Madrid once wasHulton Archive/Getty Images19 May 1939: General Franco presides over the victory parade in MadridAFP
Historians estimate as many as 500,000 combatants and civilians were killed on the Republican and Nationalist sides in the war. Atrocities were committed on both sides. The victors under General Franco executed thousands more after the war. It is estimated that over 100,000 men and women were executed and buried in unmarked graves during the conflict.