May Revolution
The May Revolution was a direct reaction to Spain's Peninsular War. In 1808, King Ferdinand VII of Spain abdicated in favor of Napoleon, who granted the throne to his brother, Joseph Bonaparte. A Supreme Central Junta led resistance to Joseph's government and the French occupation of Spain, but eventually suffered a series of reversals that resulted in the Spanish loss of the northern half of the country. On February 1, 1810, French troops took Seville and gained control of most of Andalusia. The Supreme Junta retreated to Cadiz and dissolved itself, and the Council of Regency of Spain and the Indies replaced it. News of these events arrived in Buenos Aires on May 18, brought by British ships.
Mutiny of Álzaga
Historian Bartolomé Mitre explained the mutiny of Álzaga and the May Revolution as closely related events, with the former being an antecedent of the later. This approach was rejected by Vicente Fidel López, who described Álzaga as highly pro-Spanish, decided monarchist and keeper of the Spanish integrity against the goals of the Criollos. He interpreted the events as mere domestic policy, a dispute about who was more loyal to the king, and deemed Álzaga as counter-revolutionary for acting against the goals of the factions that would eventually prevail in the May Revolution a year later. Later historians would accept López's version as canonical.