The May Revolution (Spanish: Revolución de Mayo) was a week-long series of events that took place from May 18 to 25, 1810, in Buenos Aires, capital of the Viceroyalty of the Río de la Plata. This Spanish colony included roughly the territories of present-day Argentina, Bolivia, Paraguay, Uruguay, and parts of Brazil. The result was the removal of Viceroy Baltasar Hidalgo de Cisneros and the establishment of a local government, the Primera Junta (First Junta), on May 25. The junta would eventually become the country of Argentina. It was the first successful revolution in the South American Independence process.
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.
Viceroy Cisneros tried to maintain the political status quo, but a group of criollo lawyers and military officials organized an open cabildo (a special meeting of notables of the city) on May 22 to decide the future of the Viceroyalty. Delegates denied recognition to the Council of Regency in Spain and established a junta to govern in place of Cisneros, since the government that had appointed him Viceroy no longer existed. To maintain a sense of continuity, Cisneros was initially appointed president of the Junta. However, this caused much popular unrest, so he resigned under pressure on May 25. The newly formed government, the Primera Junta, included only representatives from Buenos Aires and invited other cities of the Viceroyalty to send delegates to join them. This resulted in the outbreak of war between the regions that accepted the outcome of the events at Buenos Aires and those that did not.
The May Revolution began the Argentine War of Independence, although no formal declaration of independence was issued at the time and the Primera Junta continued to govern in the name of the deposed king, Ferdinand VII. As similar events occurred in many other cities of the continent, the May Revolution is also considered one of the early events of the Spanish American wars of independence. Historians today debate whether the revolutionaries were truly loyal to the Spanish crown or whether the declaration of fidelity to the king was a necessary ruse to conceal the true objective—to achieve independence—from a population that was not yet ready to accept such a radical change. A formal declaration of independence was finally issued at the Congress of Tucumán on July 9, 1816.