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.
First National Government
Commemorations of the May Revolution have been held since 1811, the first anniversary: Cornelio Saavedra ruled so for Buenos Aires, and Manuel Belgrano and Juan José Castelli did the same during their military campaigns at the cities they had under control during the anniversaries. The day was officially declared a national day by the Assembly of Year XIII on May 5, 1813. The 1816 Argentine Declaration of Independence provided an alternative national day. In the beginning, this added to the conflicts between Buenos Aires and the provinces in the Argentine Civil War, with the date in May being related particularly to Buenos Aires and 9 July to the whole country. This led the unitarian Bernardino Rivadavia to cancel the celebration on July, and the federalist Juan Manuel de Rosas to re-allow it, but without giving up celebrations on May. The celebrations in 1857, when Buenos Aires had temporary seceded from the Argentine Confederation, were large and included the remodelation of the Plaza. By 1880, with the federalization of Buenos Aires, the local connotations were removed and the May Revolution was considered the birth of the nation.