 He led the Buenos Aires patriots during the May Revolution, which ended with the removal of viceroy Baltasar Hidalgo de Cisneros from power.He is known as the "Speaker of the Revolution" for his speech during the open cabildo held in Buenos Aires on May 22, 1810.Castelli was appointed a Committee member of the Primera Junta and was sent to Córdoba to end Santiago de Liniers's counter-revolution.