The Revolution of 11 September 1852 was a conflict between the Province of Buenos Aires and the government of Justo José de Urquiza after the latter triumphed over Juan Manuel de Rosas at the Battle of Caseros.

A period known as "National Organization" was initiated after the Battle of Caseros. Every political faction agreed on authorizing a national Constitution. However, in opposition to the rest of the country, the ruling upper class in Buenos Aires aspired to impose political requirements on the Argentine provinces, so as to maintain the traditional political and economic preeminence of the capital city.

The result was a ten-year separation between the Argentine Confederation and the State of Buenos Aires. Both states claimed to be part of a single nation. But in reality, they behaved like separate states.

Background

After the 1819 and 1826 constitutions failed, rejected by the interior provinces due to their Unitarian Party tendencies, the Federal Party (federales) rose to power in every provincial government. Such a victory came at the cost of three decades of civil war in Argentina. Despite the absolute defeat of Unitarian factions and the death or exile of their main figures, the provinces were not able to impose a constitutional organization federally. Their chief obstacle was the province of Buenos Aires, even though all of its administrations had been federales since 1827.

During the lengthy dictatorship of Juan Manuel de Rosas, from 1835, he delayed authorization of a National Constitution until the interior provinces were at peace and well organized. This had the effect of granting numerous advantages of Buenos Aires province over the interior provinces; in particular, granting economic dominance by way of a monopoly on customs, and allowing Buenos Aires to act as the sole representative for all Argentina in foreign relations.

An alliance of sectors of the two traditional parties, the Unitarians and some Federales from the interior, and the Empire of Brazil built the Ejército Grande (Grand Army), commanded by Justo José de Urquiza, governor of the Entre Ríos, which launched an attack on Rosas and defeated him in the Battle of Caseros. All the victorious factions agreed that the next step was to establish national institutions through a Constitution. However, shortly thereafter it became evident that the Unitarians, many of whose leaders had spent years in exile and had returned in the months following the battle, aspired to maintain the hegemony of Buenos Aires.

During the first days after the Battle of Caseros, Urquiza's preeminence was accepted by everyone. He named Vicente López y Planes as deputy Governor on the 4 February. For a few weeks, an alliance of Unitarians and Federales was in charge of the provincial government, symbolized by the participation in office of Unitarian leader Valentín Alsina.

On the 11th of April, Urquiza called for elections for , from which the Unitarian parties emerged victorious. Nonetheless, López y Planes was elected Governor on 1 May. This election caused the resignation of Alsina and , Minister of War.

San Nicolás Agreement

An agreement known as the , signed 6 April (in Rosas' house) by the governors of the four coastal states, endowed Urquiza with full powers nationally, and over foreign relations. It also called for an extraordinary meeting of all provincial governors in San Nicolás de los Arroyos. Some days later, a meeting of Urquiza's followers discussed a draft agreement to be presented before the governors by In the House of Representatives, Liberals tried to discuss certain conditions to be imposed on the meeting. Ignoring that, governor López set out for San Nicolás without obtaining the authorization of the House.

Nearly all provincial governors attended the meeting in San Nicolás. On the 31 May, they signed the San Nicolás Agreement, which called for a Constituent Congress to be formed made up of two delegates from each province, with the goal of authorizing a Constitution. Among other arrangements, it was established that Representatives would attend with full power to vote their conscience, without restraint on their liberty of action, although the provinces would be able to withdraw the delegates and replace them, if necessary. The provisions for "full powers" had been used many times before by Porteño governments to pressure provincial delegates into accepting measures in opposition to the instructions given them by the provinces. The essential difference was that this time, the Congressional meeting would not take place in Buenos Aires, but in Santa Fe. This way, pressure wouldn't be applied by the Porteño government, but by the Provisional Director of the Argentine Confederation: general Urquiza himself, who paid the wages of the delegates and had put the Governor of Santa Fe in office.

Moreover, Urquiza was bestowed with the title of Provisional Director of the Argentine Confederation, so that he could establish a national government with full executive and legislative powers.

The events of June

In Buenos Aires, news about the signing of the San Nicolás Agreement provoked a reaction among the most zealous Unitarian factions. By the time governor López y Planes arrived in Buenos Aires on the 12 July accompanied by General Urquiza, the press had already shaped public opinion against the agreement. Foreshadowing what would eventually occur, an article in El Nacional ended with a striking claim from a discourse by Dalmacio Vélez Sarsfield:

In the House of Representatives, Colonel Bartolomé Mitre gave a series of speeches rejecting the agreement, with the argument that the Governor had not been authorized by the House to sign an agreement, and that powers bestowed to the Provisional Director were dictatorial.

The agreement had no defenders in the House, except for Representative and ministers Juan María Gutiérrez and Vicente Fidel López—son of the Governor. He rejected the alleged right of porteños to impose their requirements to the rest of the country, with a famous phrase:

The public, incensed against the government, hampered López from continuing his speech. The next day, assured that the agreement would be rejected, every minister resigned. A few hours later, the governor handed in his resignation as well, which was accepted immediately. The president of the legislature, the aging General Manuel Pinto, was appointed provisional Governor.

Urquiza, who was in the outskirts of Buenos Aires, reacted immediately and with energy: on the 24th of June, Pinto received a note, which read:

Urquiza also announced that the House was officially dissolved and that he was personally assuming executive powers. He also shut down various opposition periodicals, and expelled some of the top leaders from the territory, including Alsina, Mitre and Domingo Faustino Sarmiento. While he officially reinstated López in the government, López did not fully assume his powers.

Runup to revolution

López approved the agreement on behalf of the province and called for elections, in which two delegates, Salvador María del Carril and , were elected to the Congress in Santa Fe in a low-turnout election.

On 26 July, Vicente López—disagreeing with Urquiza's order to return seized property to Rosas—definitely renounced any further governing positions. Urquiza appointed himself Governor, foreshadowing what the Constitution would later name "federal intervention".

During his term as governor of Entre Rios Province, Urquiza sent doctor Santiago Derqui to Paraguay, to sign treaties of open navigation and to acknowledge the sovereignty of the country, which had been rejected previously by Rosas in 1843. Simultaneously, he announced the open navigation of interior rivers, an old grievance of the coastal provinces, which the liberal Porteños had signed on to in opposition to Rosas, for ideological reasons. But this measure brought him the hatred of old Rosas supporters, because they viewed it as the province losing its old privileges, and drew them closer to the positions of the liberals.

A tense calm held during the two months following Urquiza's coup: some of those who were exiled returned, while the city grudgingly accepted the intervention and military occupation. In public, there were no aggressive moves towards the general, and his birthday was even celebrated in Club del Progreso, but opposing parties went forward with revolutionary plans, which Urquiza confidently disregarded.

At the beginning of September, Urquiza, in a gesture of preference for his own province, handed over political power to , leader of the forces of Entre Ríos and Corrientes provinces in the city. This displeased generals Juan Madariaga and , leaders of the Corrientes troops. On 8 September, Urquiza went to Santa Fe, to open the Constituent Congress sessions.

Revolution

In the early morning of the 11th of September, most of the military forces of the city plus Galan's Correntinas troops were gathered in Plaza de Mayo, led by general José María Pirán, while , lawyer, alerted the populace by sounding the bell of the Cabildo. Various militia formations went through the city, and generals and were arrested in their homes. There were no major acts of violence, and although the situation was tense, it proceeded peacefully.

Near noon, while the troops were being given several months advance pay plus a bonus, the House of Representatives, which had been dismissed by Urquiza, reconvened, and elected General Pinto as interim governor. He named Alsina as Minister of Government and General Pirán as Minister of War.

General Galán, leadinga few military forces from Entre Ríos, withdrew first to Santos Lugares, and then toward the north of the province, from where he called Urquiza, who was getting ready to preside over the first of the Constituent Congress sessions.

A few days later, a provincial law passed granting financial rewards and rank promotions to the military involved in the revolution.

September to December

Aware of the situation in Buenos Aires, but assuming Galán was in Santos Lugares, Urquiza counter-marched up to San Nicolás, at the front of a small army from the province of Santa Fe. Upon arriving at that city, he learned of Galán's retreat and the campaign chiefs' support of the revolution; that is to say that Colonels and Jerónimo Costa, who had been stationed in the Capital, as well as the commanders of the north campaign, ; the central campaign, ; and the southern campaign, Juan Francisco Olmos, had spoken in favor of the new governor. In consequence of this, Urquiza ended his march, announcing he regretted the events, however given that the people were in agreement with the coup, he did not intend to impose his will over the will of the people of Buenos Aires. Years later, in a letter, he would explain he had judged that revolution as a movement of one circle, of one faction. When, coming closer, I perceived that the people of Buenos accepted the movement and made it theirs, I suspended the march and declared that I would leave the people of Buenos free in the exercising of their rights and in the pursuit of methods to connect with the nation in a way that its legitimate representatives would find convenient. Meanwhile, in Buenos Aires, during a meeting in the Teatro Coliseo, Alsina embraced publicly with the chief of Porteños Federals, Lorenzo Torres, who had been an ardent Rosas follower. It was the beginning of the reorganization of political parties, which would allow politicians who had followed Rosas to be reincorporated into the political scene. Also, many military leaders were reinstated in the Porteño army, in a process that had begun many months before.