The Spanish Civil War (1936–1939) broke out with a military uprising in Morocco on July 17, triggered by events in Madrid. Within days, Spain was divided in two: a "Republican" or "Loyalist" Spain consisting of the Second Spanish Republic (within which were pockets of revolutionary anarchism and Trotskyism), and a "Nationalist" Spain under the insurgent generals, and, eventually, under the leadership of General Francisco Franco. By the summer, important tendencies of the war become clear, both in terms of atrocities on both sides and in the contrast between the Soviet Union's intermittent help to the Republican government and the committed support of Fascist Italy and Nazi Germany for the Nationalists. In the early days of the war, over 50,000 people who were caught on the "wrong" side of the lines were assassinated or summarily executed. In these paseos ("promenades"), as the executions were called, the victims were taken from their refuges or jails by armed people to be shot outside of town. Probably the most famous such victim was the poet and dramatist Federico García Lorca. The outbreak of the war provided an excuse for settling accounts and resolving long-standing feuds. Thus, this practice became widespread during the war in areas conquered. In most areas, even within a single given village, both sides committed assassinations. Any hope of a quick ending to the war was dashed on July 21, the fifth day of the rebellion, when the Nationalists captured the main Spanish naval base at Ferrol in northwestern Spain. This encouraged the fascist and other sympathetic regimes of Europe to help Franco, who had already contacted the governments of Germany and Italy the day before. On July 26, the future Axis Powers cast their lot with the Nationalists. German assistance, channeled through Franco rather than to the Nationalists in general, consolidated his leadership position of the insurgency. In the north, a rebel force under Colonel Beorlegui, sent by General Emilio Mola, advanced on Gipuzkoa. On September 5, after heavy fighting, it took Irún, closing the French border to the Republicans. On September 13 the Basques surrendered San Sebastián to the Nationalists, who then advanced toward their capital, Bilbao, but were stopped at the border of the province. The capture of Gipuzkoa had isolated the Republican provinces in the north. Nationalist forces under Franco won a great symbolic victory on September 27 when they relieved the besieged Alcázar at Toledo. Two days after relieving the siege, Franco proclaimed himself Generalísimo and Caudillo ("chieftain"); he would forcibly unify the various Falangist and Royalist elements of the Nationalist cause. In October, the Nationalists launched a major offensive toward Madrid, reaching it in early November and launching a major assault on the city on November 8. The Republican government was forced to shift from Madrid to Valencia, out of the combat zone, on November 6. However, the Nationalists' attack on the capital was repulsed in fierce fighting between November 8 and 23. A contributory factor in the successful Republican defence was the arrival of the International Brigades, though only around 3,000 of them participated in the battle. Having failed to take the capital, Franco bombarded it from the air and, in the following two years, mounted several offensives to try to encircle Madrid. On November 18, Germany and Italy officially recognized the Franco regime, and on December 23, Italy sent "volunteers" of its own to fight for the Nationalists.

Detailed chronology: 1936

July

Casares Quiroga resigns as chief of the Republican government. Diego Martínez Barrio tries to form a new government, but cannot obtain broad enough parliamentary support. José Giral forms a government, which orders that arms be issued to the general populace. Seville, one of the most important cities in the south, is unsuccessfully defended by local police troops and a poorly armed workers' militia. While the heaviest weapons police possess are machine guns, the rebel General Gonzalo Queipo de Llano sends in artillery and heavily armed troops. Seville falls to the rebels. This is the day the People's Olympiad was scheduled to open in Barcelona, as a protest against the official 1936 Summer Olympics in Berlin, the capital of Nazi Germany. The games have now been cancelled due to the war. In Barcelona, heavy street-fighting breaks out between police, workers militias and loyal troops on one side and around 12,000 rebel soldiers on the other. After it becomes obvious that Civil Guard, Guardia de Asalto and City Police would not be enough to keep control of the city, the Generalitat (regional government of Catalonia), decide belatedly to arm loyal civilians. Barcelona: The combined forces of local police troops, workers' militias and citizens gain back control over the city in a dramatic two-day barricade fight. Majorca: After heavy resistance, especially at the air base, the rebels gain control over Majorca. The official leader of the uprising, General José Sanjurjo, dies in an air accident in a small aircraft bringing him back to Spain from his exile in Portugal. He had insisted, against the advice of the pilot, on taking all of his possessions with him. The overloaded aircraft crashed taking off. The Nationalist insurgents have control of the Spanish zones of Morocco, the Canary Islands, the Balearic Islands except Menorca, the part of Spain north of the Sierra de Guadarrama and the Ebro (except Asturias, Cantabria, the north of the Basque Country, and Catalonia). Among the major cities, the insurgents hold Seville, but the Republicans retain Madrid and Barcelona. Toledo: After three days of street battles against forces loyal to the government, about 1000 Civil and Assault Guards, falangists and a handful of infantry cadets, under the leadership of Colonel José Moscardó Ituarte, retreat into the Alcázar of Toledo, a stone fortress set on high ground overlooking the Tagus and the city. They take with them their own families, plus a few hundred women and children as hostages, most of them families of well-known leftists. The navy and air force remain loyal to the government. Thanks to the initiative of noncommissioned officer Benjamin Balboa, most of the Navy stayed loyal to the Republic. He was on duty in the central military radio station. As soon as he got notice of the uprising he informed the Naval Ministry and arrested his commanding officer, Captain Castor Ibáñez, then spent the night informing navy ships about the uprising. The sailors on the ships formed councils and gained control of the ships, despite heavy resistance from the officers. Spain lost three quarters of its navy officers that night, but the Navy was saved for the Republic. The officers of the Spanish Air Force are traditionally very Republican, but the air force has only a few obsolete planes. The Durruti Column, around three thousand men, mostly workers, led by Buenaventura Durruti are the first volunteer militia to leave Barcelona, heading for the Aragon front.

August

The social revolution, collectivizations. (See Spanish Revolution of 1936) At the pleading of the Marqués de Viana and the exiled ex-king of Spain, Alfonso XIII, Benito Mussolini sends aircraft in support of the rebels. Mussolini wants money for this help; the Spanish billionaire Juan March Ordinas pays for the Italian aircraft. Because Franco has no air personnel or pilots, Mussolini sends the aircraft with Italian pilots. After two of the aircraft crash on their way in the French protectorate in Morocco, the world becomes aware of this clear breach of nonintervention. General Franco arrives in Seville. While Majorca is still in hands of the nationalists, Ibiza and Formentera are back in Republican hands.

September

Nationalists have been under siege in the Alcázar de Toledo since July 21. Today, Lt. Colonel Vicente Rojo Lluch enters the Alcázar under a flag of truce to try to obtain its surrender, and failing that, the release of the hostages. Colonel Moscardo refuses both proposals. The government agree to send part of the national gold reserves to the Soviet Union. The gold is sent as security for future buying of war material from the Soviet Union. The Nationalist Junta annuls all agrarian reform that took place after the February 1936 elections. Comintern approves the creation of the International Brigades.

October

The Republican government concedes autonomy to the Basque Country (in practice, Biscay and Gipuzkoa) as Euzkadi, with José Antonio Aguirre as its president.

November–December

The Nationalists take the Madrid suburb Getafe. After a heavy attack by Moorish cavalry, tanks, and aircraft, the defenders are completely defeated. The wounded are walking disorientated over the battlefield, the organization of the defense in this area breaks down. Falangist General Varela tells foreign journalists in a press conference: "You can tell the world, Madrid will fall within one week." General Mola plans the attack route: over the Casa de Campo and the practically unpopulated University City (Ciudad Universitaria), to avoid heavy losses in the fierce street fight he would anticipate if he had to enter through the south suburbs, traditionally strong districts of the working class. Nationalist casualties are mounting but still tolerable: 115 men today. Around 1000 mostly political prisoners are massacred by their Republican Militia guards today in Paracuellos del Jarama. The prisoners, most of them accused Nationalists, were to be evacuated to Valencia from Madrid to prevent their liberation by Nationalist troops. Their Guards decide to join the defense of Madrid, kill all of the prisoners and return to Madrid.