The Day Brazilian Troops Marched Through Buenos Aires

By Brazil Stock Guide — On the morning of February 20, 1852, a porteño stepping out into central Buenos Aires would have found a city that looked familiar and yet felt distinctly unsettled. The Cabildo stood where it still stands today, facing what is now Plaza de Mayo. Once the seat of Spanish colonial administration, it had already become one of the city’s defining civic landmarks.

Low houses still lined the then Plaza de la Victoria. Horses moved through the streets. But that day there were Brazilian soldiers too. They advanced in formation, armed, accompanied by military bands and mounted officers. Above them flew the flags of the Brazilian Empire.

It was an improbable sight.

Twenty-five years earlier, almost to the day, Brazilians and men from the opposite bank of the Río de la Plata had been trying to kill one another on the plains of what is now the Brazil-Uruguay border. On February 20, 1827, at the Battle of Ituzaingó — known in Brazil as Passo do Rosário — the Imperial Army had suffered one of its most significant defeats in the Cisplatine War. The conflict ended the following year. Brazil lost the province. Uruguay emerged from it.

A quarter-century later, soldiers of the same empire were marching through the heart of Buenos Aires.

There is no evidence that the campaign had been launched to avenge Ituzaingó. Governments rarely mobilize thousands of men for reasons that romantic. Brazil was concerned with more practical matters: borders, navigation, trade, access to the province of Mato Grosso through the rivers of the Plata basin, and the possibility that Buenos Aires might become too powerful.

Two major political figures stood on opposite sides of that struggle: Juan Manuel de Rosas and Pedro II.

Rosas was not president of Argentina because, strictly speaking, Argentina did not yet exist in the form in which we understand it today. He was governor of Buenos Aires and handled the foreign affairs of the Argentine Confederation. In practice, that was enough. Buenos Aires had the port. It had the customs house. It had the money. And Rosas had Buenos Aires.

His admirers saw him as the man capable of imposing order on a collection of provinces that were often at odds with one another. His enemies preferred words such as tyrant and dictator.

For the Brazilian Empire, however, the problem was not merely Rosas’s style of rule. It was the map, and the balance of power. If Buenos Aires gained control over Uruguay and established dominant influence over Paraguay, Brazil would face a rival capable of commanding much of the Plata basin. For a continental country that was still poorly connected overland, that was a concrete strategic threat.

From Rio de Janeiro to Mato Grosso, it was often easier to sail down the Atlantic, enter the Río de la Plata and then travel upstream through the Paraná and Paraguay rivers than to cross Brazilian territory overland. The rivers were roads. And Brazil did not want Rosas holding the tollgate.

Historian Luiz Alberto Moniz Bandeira treated this struggle as part of the broader formation of the nation-states of the Plata basin. Brazil, Argentina, Uruguay and Paraguay were still defining their borders, governments, trade routes and even the practical extent of their sovereignty. The wars of the period were not simply clashes between fully formed countries. They were part of the process by which those countries were being built.

Seen from that perspective, the war against Rosas was not an imperial expedition for its own sake. It was a struggle over what kind of Argentina would emerge, whether Uruguay would remain viable, whether Paraguay would remain autonomous, and which power would dominate the rivers and governments of the southern cone.

The first battleground was Uruguay. There, a civil war seemed endless. On one side were the Blancos of Manuel Oribe, backed by Rosas. On the other were the Colorados entrenched in Montevideo. Oribe had kept the city under siege for years. Brazil decided to intervene. In 1851, Imperial troops entered Uruguay and helped break the siege. But the fatal blow against Rosas would not come from Rio de Janeiro. It would come from inside Argentina.

Justo José de Urquiza, governor of Entre Ríos, broke with Rosas. It was a dangerous rupture because Urquiza had men, horses and a strategically located province. Before long, he had assembled troops from Entre Ríos and Corrientes, Argentine exiles opposed to Rosas, Uruguayans and Brazilians. They called the force the Allied Liberating Army.

Modesty was not one of the nineteenth century’s defining virtues. The army numbered roughly 25,000 men. Only about 4,000 were Brazilian. The numbers, however, were misleading. Brazil supplied money, professional infantry, artillery, ships and logistics. Its navy moved soldiers, horses, ammunition, provisions and cannon along the rivers. It was entirely possible to be a minority on the battlefield and still be indispensable to the war effort. The Brazilian division was commanded by Brigadier Manuel Marques de Sousa, later Count of Porto Alegre. Above him in the Brazilian command structure stood Luís Alves de Lima e Silva, the future Duke of Caxias.

By early February 1852, that mixture of Argentines, Brazilians and Uruguayans had reached the outskirts of Buenos Aires. Rosas chose to fight. The battle took place at Caseros on February 3. It did not last particularly long. Urquiza’s cavalry attacked from the flanks. In the center, Brazilians, Uruguayans and Argentines moved against positions protected by Rosas’s artillery. The Imperial infantry advanced.

There was gunfire, cavalry charges, smoke, confusion and close-quarter fighting. A few hours later, it was over. The regime Rosas had built over nearly two decades collapsed in less than a morning. Rosas left the battlefield, wrote his resignation and sought British protection. Soon afterward he was aboard a ship bound for England. He never returned to power and died in Southampton in 1877.

Buenos Aires lay open. But saying that “Brazil conquered Buenos Aires” would make for a strong headline and a poor description. Most of the victorious army was Argentine. Urquiza had not defeated Rosas in order to hand his capital to Pedro II. There was no house-to-house fighting. No battle in Plaza de la Victoria. No annexation. There was something more interesting. A parade. Seventeen days after Caseros, the victors turned Buenos Aires into a stage.

The troops marched through the city center in formation. They passed through the old Plaza de la Victoria, now Plaza de Mayo, in front of the Cabildo and the buildings where porteño political power was concentrated. Accounts of the route mention Perú and Federación streets – the latter now Hipólito Yrigoyen – before the column moved toward Palermo, where Rosas had his residence.

There are no known photographs of that triumphant entry. Photography had already reached Buenos Aires, but daguerreotypes required long exposures. They were better at capturing obedient buildings than moving armies. So we know the setting, but not the exact scene. There are images of the Cabildo from that period. There are lithographs of the battle. There are later paintings. The rest has to be reconstructed. We also do not know exactly what the man standing in the square thought as the Brazilians passed.

If he opposed Rosas, perhaps he was pleased. If he had lost relatives in the war, perhaps not. Even among the former governor’s enemies, there must have been some ambivalence in watching foreign troops march armed through the center of the city. Liberation and humiliation can, occasionally, occupy the same sidewalk.

For the Brazilians, the message was simpler. The Empire had shown that it could do what no other South American state could manage at the time with the same degree of ease: finance a coalition, move troops and warships over long distances, sustain a campaign beyond its own borders and decisively alter the politics of a neighboring country.

Pedro II was 26 years old. His country was beginning to discover that it was a regional power. And then there was the date. February 20. Exactly twenty-five years after Ituzaingó. There is no need to describe the parade as official revenge to understand its symbolism. In 1827, forces of the United Provinces had defeated Brazil. In 1852, the Imperial Army was marching through Buenos Aires.

More striking still, Uruguay – whose independence had emerged from the Cisplatine War – was now fighting alongside Brazil. Yesterday’s enemies had found a new enemy. That may be one of the most durable rules of politics in the Plata basin. Alliances rarely last as long as borders. After the parade, the Brazilians left.

There was no plan to incorporate Buenos Aires into the Empire. Pedro II’s government had achieved what it wanted: Rosas was in exile, Uruguay remained independent, Paraguay had not been absorbed, and Buenos Aires could no longer shape the regional balance on its own.

Urquiza then tried to build a constitutional Argentina. Buenos Aires, naturally, disagreed. That struggle, too, was part of the formation of a nation-state. The Argentine question would only be settled after further wars between Buenos Aires and the other provinces, until a more stable central authority eventually emerged. What now looks like an obvious national border was, for decades, the product of negotiation, violence and war.

More disputes, battles and alliances followed. Thirteen years later, the political map had shifted once again. Brazil, Argentina and Uruguay would be fighting on the same side. This time against Paraguay. Francisco Doratioto, one of the leading historians of the Paraguayan War, has shown how that conflict emerged from a long struggle over regional equilibrium. Brazil, Argentina, Paraguay and Uruguay were all seeking to preserve territory, governments, trade routes and spheres of influence.

The war against Rosas belongs to the previous chapter of that same history. Caseros was not a dress rehearsal for the Paraguayan War, but some of the elements were already there: river operations, multinational armies, improbable alliances and a region in which one country’s internal affairs had a habit of becoming everyone else’s problem.

In recent months, the Paraguayan War has returned to Brazilian political debate after remarks by President Luiz Inácio Lula da Silva about the origins of the conflict. Brazil and Argentina have also resumed trading political barbs over presidents, ideology and elections.

It is tempting to look for parallels. They should not be pushed too far. Lula is not Pedro II. Milei is not Rosas. And no one is moving warships up the Paraná. Perhaps that is the reassuring part of the story. Today, when Brazilians and Argentines are angry with one another, they summon ambassadors, give interviews and post on social media. In 1852, they assembled 25,000 men.

And on a February morning, on the anniversary of an old Brazilian defeat, soldiers of the Empire marched through the square now known as Plaza de Mayo, past the Cabildo that still stands there today.