In May of 1810, word reached Buenos Aires that the King of Spain, Ferdinand VII, had been deposed by Napoleon Bonaparte. Rather than serve the new King, Joseph Bonaparte (Napoleon’s brother), the city formed its own ruling council, essentially declaring itself independent until such a time as Ferdinand could reclaim the throne. Although initially an act of loyalty to the Spanish crown, the “May Revolution,” as it came to be known, was eventually a precursor to independence. The famous Plaza de Mayo in Buenos Aires is named in honor of these actions.
Viceroyalty of the River Platte:
The lands of the eastern southern cone of South America, including Argentina, Uruguay, Bolivia and Paraguay, had been steadily growing in importance for the Spanish crown, mostly because of revenues from the lucrative ranching and leather industry in the Argentine pampas. In 1776, this importance was recognized by the establishment of a Viceregal seat in Buenos Aires, the Viceroyalty of the River Platte. This elevated Buenos Aires to the same status as Lima and Mexico City, although it was still much smaller. The wealth of the colony had made it a target for British expansion.
Left to its Own Devices:
The Spanish were correct: the British had their eye on Buenos Aires and the rich ranching land it served. In 1806-1807 the British made a determined effort to capture the city. Spain, its resources drained from the devastating loss at the Battle of Trafalgar, was unable to send any help and the citizens of Buenos Aires were forced to fight off the British on their own. This led many to question their loyalties to Spain: in their eyes, Spain took their taxes but did not hold up their end of the bargain when it came to defense.
The Peninsular War:
In 1808, after helping France overrun Portugal, Spain was itself invaded by Napoleonic forces. Charles IV, King of Spain, was forced to abdicate in favor of his son, Ferdinand VII. Ferdinand, in turn, was taken prisoner: he would spend seven years in luxurious confinement in the Château de Valençay in central France. Napoleon, wanting someone he could trust, put his brother Joseph on the throne in Spain. The Spanish despised Joseph, nicknaming him “Pepe Botella” or “Bottle Joe” because of his alleged drunkenness.
Word Gets Out:
Spain desperately tried to keep news of this disaster from reaching its colonies. Since the American Revolution, Spain had kept a close eye on its own New World holdings, fearing that the spirit of independence would spread to its lands. They believed that the colonies needed little excuse to cast off Spanish rule. Rumors of a French invasion had been circulating for some time, and several prominent citizens were calling for an independent council to run Buenos Aires while things got sorted out in Spain. On May 13, 1810, a British frigate arrived in Montevideo and confirmed the rumors: Spain had been overrun.
Buenos Aires was in an uproar. Spanish Viceroy Baltasar Hidalgo de Cisneros de la Torre pleaded for calm, but on May 18, a group of citizens came to him demanding a town council. Cisneros tried to stall, but the city leaders would not be denied. On May 20, Cisneros met with the leaders of the Spanish military forces garrisoned in Buenos Aires: they said they would not support him and encouraged him to go ahead with the town meeting. The meeting was first held on May 22 and by May 24, a provisional ruling junta which included Cisneros, Creole leader Juan José Castelli and commander Cornelio Saavedra was created.
The citizens of Buenos Aires did not want former Viceroy Cisneros to continue in any capacity in the new government, so the original junta had to be disbanded. Another junta was created, with Saavedra as president, Dr. Mariano Moreno and Dr. Juan José Paso as secretaries, and committee members Dr. Manuel Alberti, Miguel de Azcuénaga, Dr. Manuel Belgrano, Dr. Juan José Castelli, Domingo Matheu and Juan Larrea, most of whom were creoles and patriots. The junta declared itself rulers of Buenos Aires until such time as Spain was restored. The junta would last until December, 1810, when it was replaced by another one.
May 25 is the date celebrated in Argentina as the Día de la Revolución de Mayo, or "May Revolution Day." Buenos Aires' famous Plaza de Mayo, today known for protests by family members of those who "disappeared" during Argentina's military regime (1976-1983), is named for this turbulent week in 1810.
Although it was intended as a show of loyalty to the Spanish crown, the May Revolution actually started the process of independence for Argentina. In 1814 Ferdinand VII was restored, but by then Argentina had seen enough of Spanish rule. Paraguay had already declared itself independent in 1811. On July 9, 1816 Argentina formally declared independence from Spain, and under the military leadership of José de San Martín was able to defeat Spain's attempts to retake it.
Source: Shumway, Nicolas. The Invention of Argentina. Berkeley: The University of California Press, 1991.