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 Revolution
May 25 was designated as a patriotic date in 1813, but the Argentine Declaration of Independence suggests July 9 as an alternative national day. At first this added to the conflicts between Buenos Aires and the provinces during the Argentine Civil War, because the date in May related to Buenos Aires and the date of July 9 related to the whole country. Thus the unitarian Bernardino Rivadavia canceled the celebration of July 9, and the federalist Juan Manuel de Rosas allowed it again, but maintained the May celebrations. By 1880, the federalization of Buenos Aires removed the local connotations and the May Revolution was considered the birth of the nation.