In the revolts of 1930, the tenentes joined with disgruntled former officers and anti-Paulista politicians who felt that their regional interests were suffering unduly from the São Paulo-centered national state. For the tenentes , joining the Liberation Alliance (Aliança Libertadora) was a compromise of their ideals because they were locking arms with the very politicians against whom they had rebelled--former presidents Pessôa and Artur da Silva Bernardes (1922-26). This course of action was necessary, however, if the tenentes hoped to win. The alliance also included their old civilian allies: the gaucho "liberators," Paulista democrats, and Federal District (Distrito Federal) opposition politicians.

In the past, the tenentes had always sought the support of higher ranking officers. In 1930 they failed to get any generals to join them, so they settled for an up-and-coming lieutenant colonel, Pedro de Góes Monteiro, who had fought against them. In the next decade, he would reshape the army. For its part, the Liberal Alliance, led by Getúlio Dorneles Vargas, governor of Rio Grande do Sul, embraced tenente demands--such as the secret ballot, better election laws, treatment of social problems, and especially amnesty. In this way, the tenentes became one of the strong arms of the dissident oligarchies of Rio Grande do Sul, Minas Gerais, São Paulo, and Paraíba.

The revolutionaries were successful in 1930 largely because the army lost its will to defend the regime. The command structure in effect imploded, and the rebels quickly gained control of fifteen of the twenty states. The senior generals in Rio de Janeiro realized that the government was finished, and that they would be too if they did not at least keep hold of what remained of the army in the capital. Also, they were nervous that the police would lose control of the streets, so they took President Washington Luís Pereira de Sousa (1926-30) into custody. Many texts speak incorrectly of the army staging a coup and turning the government over to Getúlio Vargas. In fact, the generals were looking at defeat and acted to gain some say in the future.

Nonetheless, the senior ranks were thinned by a massive purge. By the end of 1930, nine of the eleven major generals and eleven of the twenty-four brigadier generals were retired, and in 1931 twelve of the twenty brigadier generals, many of whom had been promoted recently, also were retired. The revolution of 1930 opened a decade of reform that made the army even more an instrument of the central government and its civilian leaders.