The May Revolution (Spanish: Revolucion de Mayo) was a week-long series of events that took place from May 18 to 25, 1810, in Buenos Aires, capital of the Viceroyalty of the Río de la Plata. This Spanish colony 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 establishment of a local government, the Primera Junta (First Junta), on May 25.

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.

Viceroy Cisneros tried to maintain the political status quo, but a group of criollo lawyers and military officials organized an open cabildo (a special meeting of notables of the city) on May 22 to decide the future of the Viceroyalty. Delegates denied recognition to the Council of Regency in Spain and established a junta to govern in place of Cisneros, since the government that had appointed him Viceroy no longer existed. To maintain a sense of continuity, Cisneros was initially appointed president of the Junta. However, this caused much popular unrest, so he resigned under pressure on May 25. The newly formed government, the Primera Junta, included only representatives from Buenos Aires and invited other cities of the Viceroyalty to send delegates to join them. This resulted in the outbreak of war between the regions that accepted the outcome of the events at Buenos Aires and those that did not.

The May Revolution began the Argentine War of Independence, although no formal declaration of independence was issued at the time and the Primera Junta continued to govern in the name of the deposed king, Ferdinand VII. As similar events occurred in many other cities of the continent, the May Revolution is also considered one of the early events of the Spanish American wars of independence. Historians today debate whether the revolutionaries were truly loyal to the Spanish crown or whether the declaration of fidelity to the king was a necessary ruse to conceal the true objective—to achieve independence—from a population that was not yet ready to accept such a radical change. A formal declaration of independence was finally issued at the Congress of Tucuman on July 9, 1816.

International causes

The United States' declaration of independence from Great Britain in 1776 led criollos (Spanish peoples born in the Americas) to believe that revolution and independence from Spain were feasible. Between 1775 and 1783, the American patriots of the Thirteen Colonies waged the American Revolutionary War against both the local loyalists and the Kingdom of Great Britain, eventually establishing a popular government in the place of the British monarchy. The fact that Spain aided the colonies in their struggle against Britain weakened the idea that it would be a crime to end one's allegiance to the parent state.

The ideals of the French Revolution of 1789 spread across Europe and the Americas as well. The overthrow and execution of King Louis XVI and Queen Marie Antoinette ended centuries of monarchy and removed the privileges of the nobility. Liberal ideals in the political and economic fields developed and spread through the Atlantic Revolutions across most of the Western world. The concept of the divine right of kings was questioned by the French Declaration of the Rights of Man and of the Citizen, by the oft-quoted statement that "all men are created equal" in the United States Declaration of Independence and even by the Spanish church.

However, the spread of such ideas was forbidden in the Spanish territories, as was the sale of related books or their unauthorized possession. Spain instituted those bans when it declared war on France after the execution of Louis XVI and retained them after the peace treaty of 1796. News of the events of 1789 and copies of the publications of the French Revolution spread around Spain despite efforts to keep them at bay. Many enlightened criollos came into contact with liberal authors and their works during their university studies, either in Europe or at the University of Chuquisaca (modern Sucre). Books from the United States found their way into the Spanish colonies through Caracas, owing to the proximity of Venezuela to the United States and the West Indies.

The Industrial Revolution started in Britain, with the use of plateways, canals and steam power. This led to dramatic increases in the productive capabilities of Britain, and created a need for new markets to sell its products. The Napoleonic Wars with France made this a difficult task, after Napoleon imposed the Continental System, which forbade his allies and conquests to trade with Britain. Thus Britain needed to be able to trade with the Spanish colonies, but could not do so because the colonies were restricted to trade only with their parent state. To achieve their economic objectives, Britain initially tried to invade Rio de la Plata and conquer key cities in Spanish America. When that failed, they chose to promote the Spanish-American aspirations of emancipation from Spain.

The mutiny of Aranjuez in 1808 led King Charles IV of Spain to abdicate in favor of his son, Ferdinand VII. Charles IV requested that Napoleon restore him to the throne; instead, Napoleon crowned his own brother, Joseph Bonaparte, as the new Spanish King. These events are known as the Abdications of Bayonne. Joseph's coronation was met with severe resistance in Spain, which started the Peninsular War, and the Supreme Central Junta took power in the name of the absent king. This also led to Spain switching allegiances from France to Britain. France eventually invaded Sevilla, and a Council of Regency based in Cadiz replaced the disbanded Supreme Central Junta.

National causes

Spain forbade its American colonies to trade with other nations or foreign colonies, and imposed itself as the only buyer and vendor for their international trade. This situation damaged the viceroyalty, as Spain's economy was not powerful enough to produce the huge supply of goods that the numerous colonies would need. This caused economic shortages and recession. The Spanish trade routes favored the ports of Mexico and Lima, to the detriment of Buenos Aires. As a result, Buenos Aires smuggled those products that could not be obtained legitimately. Most local authorities allowed this smuggling as a lesser evil, even though it was illegal, and it occasionally equalled in volume the legal commerce with Spain. Two antagonistic factions emerged: the landowners wanted free trade so they could sell their products abroad, while the merchants, who benefited from the high prices of smuggled imports, opposed free trade because prices would come down.

The coronation of Infanta Carlota Joaquina was considered an alternative to revolution.

The Spanish monarchy appointed their own candidates to most of the political offices in the viceroyalty, usually favoring Spaniards from Europe. In most cases, the appointees had little knowledge of or interest in local issues. Consequently, there was a growing rivalry between criollos and peninsulars (those born in Spain). Most criollos thought that peninsulars had undeserved advantages and received preferential treatment in politics and society. The lower clergy had a similar sentiment about the higher echelons of the religious hierarchy. Events developed at a slower pace than in the United States independence movement. This was in part because the clergy controlled the entire educational system in Spanish America, which led the population to hold the same conservative ideas and follow the same customs as in Spain.

Buenos Aires and Montevideo successfully resisted two British invasions. In 1806, a small British army led by William Carr Beresford seized Buenos Aires for a brief time; a Montevidean army led by Santiago de Liniers liberated the city. The following year, a larger army seized Montevideo, but was overwhelmed by the forces of Buenos Aires; the invaders capitulated and returned Montevideo to the viceroyalty. There was no aid from Spain during either invasion. Liniers organized criollo militias during the preparations for the second invasion, in spite of the prohibition against them. The Patricios Regiment, led by Cornelio Saavedra, was the biggest criollo army. These events gave criollos military power and political influence that they did not have before and, since the victory was achieved without any help from Spain, it boosted criollo confidence in their independent capabilities.

The Portuguese royal family left Europe and settled in colonial Brazil in 1808, after their escape from the Napoleonic invasion of Portugal. Carlota Joaquina, sister of Ferdinand VII, was the wife of the Portuguese prince regent, but had her own political projects. As she avoided the later capture of the Spanish royal family, she attempted to take charge of the viceroyalty as regent. This political project, known as Carlotism, sought to prevent a French invasion of the Americas. A small secret society of criollos, composed of politicians such as Manuel Belgrano and Juan Jose Castelli, and military leaders such as Antonio Beruti and Hipolito Vieytes, supported this project. They considered it an opportunity to get a local government instead of a European one, or a step towards a potential declaration of independence. The project was resisted by Viceroy Liniers, most peninsulars, and some criollos, including Cornelio Saavedra and the lawyers Mariano Moreno and Juan Jose Paso. They suspected that it concealed Portuguese expansionist ambitions over the region. The supporters of Carlota Joaquina intended her to head a constitutional monarchy, whereas she wanted to govern an absolute monarchy; these conflicting goals undermined the project and led to its failure. Britain, which had a strong influence in the politics of the Portuguese Empire, opposed the project as well: they did not want Spain split into several kingdoms, and considered Carlota Joaquina unable to prevent this.

Buenos Aires endured the whole Spanish American Wars of independence without being reconquered by royalist armies or successful royalist counter-revolutions. However, it faced several internal conflicts. The May Revolution lacked a clear leader as other regions of Latin America; the secretary Mariano Moreno led the initial phase of the government, but he was removed shortly afterwards.

The Council of Regency, the Royal Audiencia of Buenos Aires and the peninsulars opposed the new situation. The Royal Audiencia secretly swore allegiance to the Council of Regency a month later and sent communiques to the other cities of the Viceroyalty, to request them to deny recognition to the new government. To put an end to these activities, the Junta assembled Cisneros and all the members of the Royal Audiencia on the pretext that their lives were in danger, and sent them into exile aboard the British ship Dart. Captain Mark Brigut Larrea was instructed to avoid American ports and deliver all of them directly to the Canary Islands. The Junta then appointed a new Audiencia composed entirely of criollos loyal to the revolution.

Every city in the territory of modern Argentina other than Cordoba endorsed the Primera Junta. The cities of the Upper Peru, however, did not take a position, owing to the recent outcomes of the Chuquisaca and La Paz Revolutions. Asuncion del Paraguay rejected the Junta and swore loyalty to the Council of Regency. The Banda Oriental, under Francisco Javier de Elío, remained a royalist stronghold.

Former Viceroy Santiago de Liniers organized a counter-revolution in Cordoba, and this became the first military campaign of the independent government. Despite the importance of Liniers himself, and his prestige as a popular hero for his role when the British invaded, the population of Cordoba preferred to support the revolution. This reduced the power of the counter-revolutionary army by means of desertions and sabotage. Liniers's troops were quickly defeated by the forces led by Francisco Ortiz de Ocampo. Ocampo refused to shoot the captive Liniers; hence the execution ordered by the Junta was carried out by Juan Jose Castelli. After the victory, the Primera Junta sent military expeditions to many other cities, to demand support and the election of representatives to it.

Mariano Moreno was an influential member of the Primera Junta.

Montevideo, which had a historical rivalry with Buenos Aires, opposed the Primera Junta and the Council of Regency declared it the new capital of the Viceroyalty, along with Francisco Javier de Elío as the new Viceroy. The city was well defended, so it could easily resist an invasion. Peripheral cities in the Banda Oriental acted contrary to Montevideo's will and supported the Buenos Aires Junta. Jose Gervasio Artigas led them, and kept Montevideo under siege. The final defeat of the Montevidean royalists was carried out by Carlos María de Alvear and William Brown.

The Captaincy General of Chile followed a process analogous to that of the May Revolution, and elected a Government Junta that inaugurated the brief period known as Patria Vieja. The Junta was defeated in 1814 at the Battle of Rancagua, and the subsequent Reconquista of Chile would make it a royalist stronghold once more. The Andes provided an effective natural barrier between the Argentine revolutionaries and Chile, so there was no military confrontation between them until the Crossing of the Andes, led by Jose de San Martín in 1817, a campaign that resulted in the defeat of the Chilean royalists.

The Primera Junta increased in size when it incorporated the representatives sent by the provinces. From then on, the Junta was renamed the Junta Grande. It was dissolved shortly after the June 1811 defeat of the Argentine troops at the Battle of Huaqui, and two successive triumvirates exercised executive power over the United Provinces of the Río de la Plata. In 1814, the second triumvirate was replaced by the authority of the Supreme Director. Meanwhile, Martín Miguel de Güemes contained the royalist armies sent from the Viceroyalty of Peru at Salta, while San Martín advanced towards the royalist stronghold of Lima by sea, on a Chilean–Argentine campaign. The war for independence gradually shifted towards northern South America. From 1814, Argentina descended into civil war.