The bombing of São Paulo, which took place during the São Paulo Revolt of 1924, was the largest artillery and air attack in São Paulo's history. From 5 to 28 July 1924, rebel and loyalist forces used bombing in their fight for the city; the rebels had up to 26 artillery pieces from the Brazilian Army, while the loyalists had more than a hundred guns and six bombers from the Army Aviation. Artillery, and especially loyalist artillery, was largely responsible for the conflict's casualties, most of whom were civilians.
The rebels had the artillery advantage in the early days and had been firing since the morning of 5 July. From positions such as Campo de Marte and Cemitério do Araçá, they aimed their 75 and 105 mm Krupp cannons at the Campos Elíseos Palace, headquarters of governor Carlos de Campos, the headquarters of the 4th Battalion of the Public Force of São Paulo, and other loyalist targets. Mistakes in aim cost the lives of several civilians, but the pressure on the governor contributed to the withdrawal of loyalist troops to the outskirts of the city on 8 July. General Eduardo Sócrates' loyalist division received continuous reinforcements, gaining a strong advantage in artillery, with more recent designs from Schneider and Saint Chamond, including the conflict's most powerful 155 mm artillery.
On the sides of Penha and Ipiranga, the divisional artillery launched intense attacks beginning on 11 July, targeting mainly the working-class neighborhoods in the south and east of the city, such as Brás, Belenzinho and Mooca, where the loyalist troops were trying to advance. Loyalist bombardment destroyed some defensive strongholds, such as factories, but was generally ineffective; loyalist general Abílio de Noronha criticized the bombardment in technical terms as a haphazard attack, without regulation and correction of fire, destroying mainly civilian targets. The population was terrorized, hiding in cellars and leaving the city by the hundreds of thousands. Foreign diplomatic representatives and São Paulo's economic elite, harmed by the chaos in the city, tried to negotiate an interruption in the bombings, but the government did not give in. The bombing had the full endorsement of president Artur Bernardes and governor Carlos de Campos, who was the author of the expression: "São Paulo would rather see its beautiful capital destroyed than legality in Brazil destroyed".
1,800 buildings were damaged in the conflict, among which the Theatro Olympia, the Glória Church, the Cotonifício (Cotton Factory) Crespi, and the Duchen Biscuits Factory are emblematic. The bombing was very controversial at the time and has a negative impact on the image of Artur Bernardes in historiography. The brutality of the bombing is compared to previous conflicts in Brazil like the War of Canudos, and the government is accused of deliberately attacking civilians in a "terrorizing bombing", either as punishment for the population of working-class neighborhoods or as pressure to force the rebels to withdraw – which they did on 27 July. The legality of the bombing has been contested since 1924, as international law at the time already condemned the bombing of a city without regard for civilian lives, which could constitute a war crime.
Background
On 5 July 1924, lieutenant revolutionaries of the Brazilian Army and the Public Force of São Paulo, led by retired general Isidoro Dias Lopes, started a military uprising in São Paulo, planning a rapid takeover of the city to then advance towards Rio de Janeiro and depose president Artur Bernardes. The rebels did not gain all the expected troop support and soon found themselves locked in urban combat against loyalist forces. The first days of fighting were concentrated in Campos Elíseos, Luz and in the historic center. The loyalists retreated to the outskirts of the city on 8 July, grouping in the directions of Santos and Rio de Janeiro, with the seat of the state government being transferred to the Guaiaúna railway station, in Penha.
Against 3 to 3,500 rebels, the federal government brought reinforcements from other states, forming a loyalist army of 14–15,000 men, armed with the most modern equipment available in the country, with which the reconquest of the city began. The crossfire took place in the working-class neighborhoods. The loyalists reoccupied the city on 28 July, after an overnight evacuation by the rebels, who seized the railroads on their way to the Paraná River, prolonging the revolt inland.
Weapons used
Several types of army artillery were used in the combats in São Paulo, with 75, 105 and 155 millimeters caliber guns. Most of the pieces dated from the beginning of the century; the most modern ones were bought after the First World War, under the influence of the French Military Mission. The guns were transported by animal traction; it was not until the 1930s that the Brazilian Army began to use motorized transport for its guns.
The 75mm Krupp artillery existed in two models of field guns (C/28, 1905 model, and C/28, 1908 model), one of mountain guns (C/14, model 1906), and one of howitzers (C /14, 1906 model). The 1908 field cannon fired seven-kilogram shell, of the high-explosive type, for the destruction of houses, and shrapnel, for anti personnel. Its range was 6.8 kilometers. The mountain cannon was similar, but could be broken down into bales for transport on the back of mules. Its ammunition was the same, but with a smaller case and protective charge. It had a range of three kilometers and poorer aim. The army also had 75mm C/36 1920 Model field guns from Saint-Chamond and C/18.6 1919 Model mountain guns from Schneider.
105mm Krupp guns from 1910 fired fifteen kilogram shells in direct and indirect fire up to four miles away. Each shell could damage structures or, due to shrapnel, kill people within 400 meters of the hit point. The army's most powerful artillery pieces were the 155 mm howitzers, 1917 model, by Schneider, whose shots had a range of up to eleven kilometers, and could kill a person within a 600-meter radius from the hit point.
The army's infantry had guns of lesser firepower to directly accompany their attacks: Stokes mortars and 37mm Puteaux revolver-cannons. The 37 mm guns had an effective range of 1,500 meters. The Brazilian Navy also contributed 16 small-caliber rapid-fire cannons, installed in railway wagons at the Companhia Docas de Santos' workshops. They were 38mm Nordenfelt, 47mm Armstrong, and 57mm Nordenfelt models, taken from the Naval Academy and navy battleships. This railway artillery was used to attack Mooca through the tracks of the São Paulo Railway Company.
The rebels' greatest firepower consisted of twenty 75 mm and six 105 mm guns, all from Krupp. The first loyalist artillery arrived on 7 July: two 75mm Armstrong guns from the navy and two 75 mm Krupp guns from the army. These pieces' range was inferior to that of the rebel artillery, which managed to fire against the loyalist pieces. Throughout the month, the loyalist artillery was reinforced and achieved qualitative and quantitative superiority, with Schneider and Saint Chamond guns of up to 155mm. The heavy and outdated cannons in the hands of the rebels did not have the range to reach the more than 100 loyalist guns, well positioned in the hills on the outskirts of the city.
Both sides employed military aviation, but the rebels' only bombing mission was an unsuccessful attempt on the Catete Palace in Rio de Janeiro. The loyalists had six Breguet 14A2/B2 bombers from Army Aviation. They dropped over a hundred small grenades and at least three 75-kilogram bombs on the city.
Hierarchical responsibility
The artillery units present in the state of São Paulo in July 1924, in the 2nd Military Region, were the 2nd Independent Group of Heavy Artillery (GIAP), in Quitaúna, Osasco; the 2nd Mountain Artillery Group (GAM), in Jundiaí; the 4th Horse Artillery Regiment (RAM), in Itu; and the 3rd Coastal Artillery Group, at the Itaipu Fort, Praia Grande. All of these units, plus several groups and regiments from other military regions, took part on one side or the other in the revolt.
Lieutenant Custódio de Oliveira, from the 2nd GIAP, was instrumental in the lieutenant conspiracy and subsequent revolt. The outbreak of the revolt depended on his battery, whose position to be occupied in the city was defined months in advance. Oliveira moved his battery at dawn, simulating an exercise, and, with some delay, was already positioned in the capital of São Paulo in the morning. The 2nd GAM, belonging to lieutenant colonel Olinto de Mesquita Vasconcelos, came to São Paulo to join the revolt the following day. After the withdrawal of the state government, the 4th RAM, under captain Clístenes Barbosa, did the same.
Loyalist artillery units formed part of the Division of Operations in the State of São Paulo, commanded by general Eduardo Sócrates, in which they formed part of one of its infantry brigades or served as divisional troops. Its order of battle was published shortly after the revolt by writers Ciro Costa and Eurico de Góis, based on official notes from the military commands, and by general Abílio de Noronha, commander of the 2nd Military Region at the start of the revolt. The two listings have some differences:
+Divisional troops: 1st Heavy Artillery Group (one battery of 155 mm and another of 105 mm guns) 6th Mounted Artillery Regiment 5th Mountain Artillery Group 3rd Heavy Artillery Group (one battery)
In colonel João Gomes Ribeiro's brigade: 75mm battery of the 9th Mounted Artillery Regiment
In general Carlos Arlindo's brigade: 3rd Coastal Artillery Group (one battery) Navy's force, including its artilleryDivisional Artillery Brigade (General João José de Lima) 8th Mounted Artillery Regiment (Colonel Crisanto Leite de Miranda Sá Júnior) 2nd Group of the 1st Mounted Artillery Regiment (Major Mascarenhas de Morais) 2nd Heavy Artillery Regiment (Lieutenant Colonel Alfredo Assunção) 3rd Battery of the 9th Mounted Artillery Regiment(Captain Reis Júnior)
In general Carlos Arlindo's brigade: 3rd Independent Heavy Artillery Group (Captain Argemiro Dornellas) 1st Horse Artillery Group(Lieutenant Colonel Bento Marinho Alves) 9th Battery of the 6th Mounted Artillery Regiment(Captain Pedro Duro)
The loyalist bombers came from the Aviation School of Campo dos Afonsos, in Rio de Janeiro, whose commander, lieutenant colonel Álvaro Octávio de Alencastre, served as Director of Aeronautics in operations against the revolt. The commander of the pilots and aerial observers was captain Marcos Evangelista da Costa Villela Júnior.
The effective command of the army was disputed between the Chief of Staff of the Army and the Minister of War, both, in practice, appointed by the president of Brazil. The bombing was carried out with the approval of Minister of War Setembrino de Carvalho and president Artur Bernardes. Thus, the responsibility fell to the federal government. The state government of Carlos de Campos supported the president's decision.
Bombed areas
By the rebels
On the morning of 5 July, the 2nd GIAP's 105 mm guns were positioned by the rebels on Campo de Marte. From there, they fired the first artillery shots of the conflict, after 09:00, aimed at the Campos Elíseos Palace, seat of the state government, where the loyalist forces focused their defensive effort. The bombardment was supposed to break the defenders' resistance,, “Os rebeldes também bombardearam a cidade” but it did not intimidate the governor to leave the palace or even to take refuge in the cellars.