The May Revolution happened from May 18 to 25, 1810, in Buenos Aires. Buenos Aires was the capital of the Viceroyalty of the Río de la Plata. It was a Spanish colony that included roughly the territories of present-day Argentina, Bolivia, Paraguay and Uruguay. The result was the removal of Viceroy Baltasar Hidalgo de Cisneros and the forming of a local government now called the "Primera Junta". In Argentina this is now celebrated as "May Week" (Spanish: Semana de Mayo).
The May Revolution was a direct reaction to Spain's Peninsular War of the previous two years. In 1808, King Ferdinand VII of Spain abdicated in favor of Napoleon. Napoleon gave the throne to his brother, Joseph Bonaparte.
The May Revolution began the Argentine War of Independence. No formal declaration of independence was made. The Primera Junta continued to govern in the name of the deposed king, Ferdinand VII. The Argentine Declaration of Independence was made at the Congress of Tucumán on July 9, 1816.