Brazilian Integralism, led by Plínio Salgado, had been gaining strength since its founding in 1932. Modeled on European fascist movements, the Integralists wore green shirts, used the sigma symbol, and adopted the raised-arm salute. Their growth alarmed leftists across São Paulo. On June 25, 1933, the Antifascist United Front — the Frente Única Antifascista, or FUA — was founded, bringing together an unlikely coalition. The Communist League, the Brazilian Socialist Party, Italian anti-fascist exiles, anarchist newspapers like A Lanterna and A Plebe, and the Workers' Federation of São Paulo (FOSP) all joined under one banner. When word spread that the Integralists intended to march through the city center, these groups resolved to stop them.

Praça da Sé sits at the geographic and symbolic center of São Paulo — the point from which all distances in the city are measured. The square fronts the massive neo-Gothic cathedral, whose construction had begun in 1913 and was still years from completion in 1934. Into this space, thousands of Integralists gathered for their rally. The anti-fascist counter-demonstrators arrived without central leadership, a loose assembly of workers, students, and activists. Accounts differ on who fired first, but the confrontation escalated rapidly from shoving to shooting. When it ended, three Integralists, one anti-fascist student, two police officers, and a civil guard lay dead. The square that had hosted religious processions and political speeches for centuries had become a site of ideological violence.

Among the dead was Tobias Warchavski, a young anti-fascist militant. The identification of his body galvanized public opinion in ways the battle itself had not. His death triggered a political campaign against the repressive policies of President Getúlio Vargas, whose government had tolerated — and at times tacitly supported — the Integralist movement. The emotional response to Warchavski's killing helped drive the formation of the National Liberation Alliance (ANL), a broad progressive front that would become one of the most significant political coalitions of 1930s Brazil. Meanwhile, police raided and sealed the FOSP headquarters, arresting leftist militants. The anarchists who had helped organize the anti-fascist resistance formed the Social Prisoners Committee, holding fundraising events to support jailed comrades and their families.

The battle's aftermath played out not just in courtrooms and political halls but in the press. In Rio de Janeiro, the satirical newspaper Jornal do Povo — edited by Aparício Torelly and linked to the Brazilian Communist Party — devoted its first issue, published on October 7, to mocking the Integralists' retreat. One headline read: "An Integralist Doesn't Run, It Flies." Beneath an image of the chaos in Praça da Sé, the paper described "the integralist stampede, in the most perfect disorder" and jibed at the green-shirted marchers cowering behind poles. The satirical treatment of the Integralists' rout helped cement the battle as a symbolic victory for the left, even as the political repression that followed suggested a more ambiguous outcome.

The Battle of Praça da Sé did not happen in isolation. Two years later, in London's East End, anti-fascists would block Oswald Mosley's Blackshirts in the Battle of Cable Street. In Paris, the February 6, 1934, crisis had already pitted far-right leagues against the French Republic. São Paulo's confrontation belongs to this global wave of 1930s anti-fascist resistance, a period when ordinary citizens chose to physically confront movements they believed threatened democratic society. Today, Praça da Sé remains one of the city's most important public spaces — a place where São Paulo's political passions have always found expression, from cathedral dedications to street battles to the demonstrations that continue to fill the square.