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.
May Conspiracy
In March 1849, Mikhail Bakunin, a Russian Pan Slavic revolutionary, visited Prague and suggested to organize an armed uprising in Prague and several German-speaking cities as a response to post-1848 political reaction. The date of the uprising was set on May 12, 1849, but due to amateurish organization police took the organizers into custody on the night of May 9 to May 10 1849.