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.
British invasions of the River Plate
The social effects of the invasions are among the causes of the May Revolution. The criollos, who had so far been denied important positions, could get political strength through military roles. The successful resistance with little help from Spain fostered the desire for self-determination. An open cabildo and the Royal Audience of Buenos Aires deposed the viceroy Rafael de Sobremonte and designated instead the French popular hero Santiago de Liniers, which was a completely unprecedented action: before that, the viceroy was only subject to the King of Spain himself, and no one from the colonies had authority over him.