structural:summarization, structural:reformatting
Nationalists

Nationalist atrocities, which authorities frequently ordered so as to eradicate any trace of "leftism" in Spain, were common. The notion of a limpieza (cleansing) formed an essential part of the rebel strategy, and the process began immediately after an area had been captured. Estimates of the death toll vary; historian Paul Preston estimates the minimum number of those executed by the rebels as 130,000, while Antony Beevor places the figure much higher at an estimated 200,000 dead. The violence was carried out in the rebel zone by the military, the Civil Guard and the Falange in the name of the regime. Julius Ruiz reports that the Nationalists killed 100,000 people during the war and executed at least 28,000 immediately after. The first three months of the war were the bloodiest, with 50 to 70 percent of all executions carried out by Franco's regime, from 1936 to 1975, occurring during this period. The first few months of killings lacked much in the way of centralisation, being largely in the hands of local commanders. According to Stanely Payne and Jesús Palacios, General Mola was taken aback by them, despite his own planning emphasising the need for violence; early in the conflict he had ordered a group of leftist militiamen to be immediately executed, only to change his mind and rescind the order.

Many such acts were committed by reactionary groups during the first weeks of the war. This included the execution of schoolteachers, because the efforts of the Second Spanish Republic to promote laicism and displace the Church from schools by closing religious educational institutions were considered by the Nationalists as an attack on the Roman Catholic Church. Extensive killings of civilians were carried out in the cities captured by the Nationalists, along with the execution of unwanted individuals. These included non-combatants such as trade-unionists, Popular Front politicians, suspected Freemasons, Basque, Catalan, Andalusian, and Galician Nationalists, Republican intellectuals, relatives of known Republicans, and those suspected of voting for the Popular Front. The Nationalists also frequently killed military officers who refused to support them in the early days of the coup. Many killings in the first few months were often done by vigilantes and civilian death squads, with the Nationalist leadership often condoning their actions or even assisting them. Post-war executions were conducted by military tribunal, though the accused had limited ways to defend themselves. A large number of the executed were done so for their political activities or positions they held under the Republic during the war, though those who committed their own killings under the Republic were also amongst executed as well. A 2010 analysis of Catalonia argued that Nationalist executions were more likely to occur when they occupied an area that experienced greater prior violence, likely due to pro-Nationalist civilians seeking revenge for earlier actions by denouncing others to the Nationalist forces. Michael Seidman argues that the Nationalists' greater death toll may be partially attributable to their military success resulting in territorial gains and thus more opportunities to enact violence against their enemies. However, during the war, executions declined as the Francoist state began to establish itself.

Nationalist forces massacred civilians in Seville, where some 8,000 people were shot; 10,000 were killed in Cordoba; 6,000–12,000 were killed in Badajoz after more than 1,000 landowners and conservatives were killed by the revolutionaries. In Granada, where working-class neighbourhoods were hit with artillery and right-wing squads were given free rein to kill government sympathizers, at least 2,000 people were murdered. In February 1937, over 7,000 were killed after the capture of Málaga. When Bilbao was conquered, thousands of people were sent to prison. There were fewer executions than usual, however, because of the effect Guernica left on Nationalists' reputations internationally. The numbers killed as the columns of the Army of Africa devastated and pillaged their way between Seville and Madrid are particularly difficult to calculate. Landowners who owned the large estates of Southern Spain rode alongside the Army of Africa to reclaim via force of arms the land given to the landless peasants by the Republican government. Rural workers were executed, and it was mockingly joked that they had received their "land reform" in the form of a burial plot.

Nationalists also murdered Catholic clerics. In one particular incident, following the capture of Bilbao, they took hundreds of people, including 16 priests who had served as chaplains for the Republican forces, to the countryside or graveyards and murdered them.

Franco's forces also persecuted Protestants, including murdering 20 Protestant ministers. Franco's forces were determined to remove the "Protestant heresy" from Spain. The Nationalists also persecuted Basques, as they strove to eradicate Basque culture. According to Basque sources, some 22,000 Basques were murdered by Nationalists immediately after the Civil War.

The Nationalist side conducted aerial bombing of cities in Republican territory, carried out mainly by the Luftwaffe volunteers of the Condor Legion and the Italian air force volunteers of the Corpo Truppe Volontarie: Madrid, Barcelona, Valencia, Guernica, Durango, and other cities were attacked. The Bombing of Guernica was the most controversial. The Italian air force conducted a particularly heavy bombing raid on Barcelona in early 1938. While some Nationalist leaders did oppose the bombing of the city—for example, Generals Yagüe and Moscardó, who were noted for being nonconformists, protested against the indiscriminate destruction—other Nationalist leaders, often those of a fascist persuasion, approved of the bombings which they saw as necessary to "cleanse" Barcelona.

Michael Seidman observes that the Nationalist terror was a key part of the Nationalist victory as it allowed them to secure their rear; the Russian Whites, in their civil war, had struggled to suppress peasant rebellions, bandits and warlordism behind their lines; British observers argued that if the Russian Whites had been able to secure law and order behind their lines, they would have won over the Russian peasantry, while the inability of the Chinese Nationalists to stop banditry during the Chinese Civil War did severe damage to the regime's legitimacy. The Spanish Nationalists, in contrast, imposed a puritanically terrorist order on the populace in their territory. They never suffered from serious partisan activity behind their lines and the fact that banditry did not develop into a serious problem in Spain, despite how easy it would have been in such mountainous terrain, demands explanation. Seidman argues that severe terror, combined with control of the food supply, explains the general lack of guerilla warfare in the Nationalist rear. A 2009 analysis of Nationalist violence argues that evidence supports the view that killings were used strategically by the Nationalists to pre-emptively counter potential opposition by targeting individuals and groups deemed most likely to cultivate future rebellions, thus helping the Nationalists win the war.