May Revolution
The mutiny of Aranjuez in 1808 led King Charles IV of Spain to abdicate in favor of his son, Ferdinand VII. Charles IV requested that Napoleon restore him to the throne; instead, Napoleon crowned his own brother, Joseph Bonaparte, as the new Spanish King. These events are known as the Abdications of Bayonne. Joseph's coronation was met with severe resistance in Spain, which started the Peninsular War, and the Supreme Central Junta took power in the name of the absent king. This also led to Spain switching allegiances from France to Britain. France eventually invaded Sevilla, and a Council of Regency based in Cadiz replaced the disbanded Supreme Central Junta.
Juan José Castelli
When the news of the fall of the Junta of Seville arrived, the group headed by Castelli and Belgrano led the process leading to the May Revolution. Castelli and Saavedra were the most important leaders of the time, and first discarded Martín Rodríguez's plan to expel Cisneros in a coup d'état. After several discussions, they decided to request an open cabildo, an emergency popular assembly. Castelli and Belgrano negotiated with the senior alcalde and nobleman, Juan de Lezica, and the procurator, Julián de Leiva. Although they convinced them, they still needed the permission of Cisneros himself, for which Castelli and Rodriguez went to his office at the Fort of Buenos Aires. Previously, Cornelio Saavedra had denied Cisneros the support of the Regiment of Patricians, on the premise that with the disappearance of the Junta of Seville—who had appointed him as viceroy—he no longer had the right to hold that position.