Battle of San Nicolás The Battle of San Nicolás was a naval engagement on 2 March 1811 on the Paraná River between the Spanish royalists from Montevideo , and the first flotilla created by the revolutionary government of Buenos Aires . It was the first engagement between the two fleets in the River Plate region since the revolution . It was a royalist victory . Precedent . On May 25 , 1810 the River Plate colonies revolted against the Spanish Viceroy at the May Revolution in Buenos Aires , claiming the necessity of assuming local government due to the difficult situation in Spain , which was occupied by Napoleonic troops . The royalist authorities in Montevideo opposed the measure and declared a naval blockade of Buenos Aires . In the city of Montevideo , there was a navy base serving as port for the royal Spanish fleet in the South American Atlantic coast . The local Junta Grande ( Buenos Aires ' revolutionary government ) decided to establish a fleet to contest the Spanish dominion of the local waters . Creation of the rebel fleet . The Junta Grande which took control of the government in Buenos Aires named Francisco de Gurruchaga , as secretary of the Navy . He immediately set to work to create a small naval fleet . With effort , Gurruchaga bought five vessels of different types from local owners , and equipped three of them with artillery , which had been taken for the most part out of service as obsolete . He obtained a schooner , a brigantine and a sloop , christened respectively " " Invencible " " , " " 25 de Mayo " " and " " América " " . Recruiting of the crew was another difficult endeavor , as the inhabitants of the pampas were not used to a sailor ' s life . The solution was to hire foreigners , who for the most part did not speak Spanish . The rank and file was filled with locals . Command of the flotilla was given to a Maltese privateer , Lieutenant Colonel Juan Bautista Azopardo . This sailor had arrived in the River Plate at the beginning of the 19th century , and had participated in the British invasions of the Río de la Plata of 1806 and 1807 . Azopardo commanded the " Invencible " , seconded by Hipólito Bouchard on " 25 de Mayo " , and Ángel Hubac , on " América " . The first mission . At the beginning of 1811 the Junta Grande was immersed in armed conflicts in various fronts against counter - revolutionary ( royalist ) forces . A small army under the command of Manuel Belgrano had been sent to Paraguay to help the locals join the revolution , but after an initial victory at the Battle of Campichuelo , he was defeated at the Battle of Paraguarí and was forced to retreat . The Junta decided to respond to the reinforcement request from Belgrano , and tasked Azopardo with the transport by river of the reinforcement troops and artillery to Paraguay . The Maltese raised his flag in the " " Invencible " " , while the Frenchman naturalized Argentine Hipólito Bouchard was put in charge of the brigantine " " 25 de Mayo " " . Lastly , the sloop " " América " " was put under the command of the Frenchman Abel Hubac . The royalist authorities in Montevideo learned of these plans and detached a flotilla to intercept the rebels . The mission was given to Jacinto Romarate , an able officer , who could deploy seven small warships of superior quality , and firepower than his enemy ' s . The Battle of San Nicolás . Azopardo ' s flotilla left Buenos Aires , going upriver on the Paraná . Arriving near San Nicolás they saw the royalists and Azopardo decided to do battle . The rebel commander order a battery of cannons were removed from the ships and installed on the coast , and that a regiment of sailors and militias made ready to fight from the river coast . On March 2 they fought , when the royalist ships closed in the rebels . In the first encounter , two royalist brigantines ( " " Belén " " and " " Cisne " " ) became groudned near the coast and were made targets for the coastal cannons and the rebel infantry . Nonetheless , Azopardo could not get to board them and the ships finally freed themselves and retreated . After several hours the royalists tried a new attack , and shot at the " " Invencible " " . The " " América " " was hit several times , with a gash opening on her prow , beginning to take on water , and had to be abandoned by the crew . The royalists then concentrated on the " " 25 de Mayo " " , which they tried to board ; the poorly trained crew became panicked and abandoned ship jumping overboard , against the attempts of Bouchard to stop them . The royalist vessels closed in on the " " Invencible " " , which was by now fighting on her own , and boarded her . The crew fought valiantly for almost two hours until the situation became unsustainable . Azopardo tried to blow up the munitions depot , but the wounded begged him not to do it , so he was forced to surrender . Consequences . The defeat caused the destruction of the rebel fleet and the taking control over the Rio de la Plata , Paraná and Uruguay rivers by the royalist fleet from Montevideo ; which would last until 1813 with the creation of a new naval squadron and the victories of William Brown . For the moment , it meant that the reinforcements requested by general Belgrano did not arrive . A few days after the battle at San Nicolás , Belgrano ' s army was attacked and defeated at the Battle of Tacuarí ( March 9 , 1811 ) . Juan Bautista Azopardo became a prisoner of the royalists and was taken to Ceuta , Spain . The revolutionary government in Buenos Aires , still started a judicial process " in absentia " to determine his involvement in the defeat . The report obtained recognized Azopardo ' s courage , but concluded he had demonstrated lack of experience in command and that he had allowed lack of discipline on his crew . The sentence given was the indefinite inhabilitation of command in the armed forces , establishing that he could only serve as a subordinate officer . Azopardo confronted while imprisoned in Spain charges of adhering to the revolutionary cause ; and was condemned to death to later have his sentenced commuted . Finally in 1820 , the liberal movement in Spain headed by general Rafael de Riego freed all political prisoners including Azopardo allowing him to return to South America . The following year , Buenos Aires rescinded his inabilitation order and allowed him to return to military life in the Argentine Navy . The governing Junta communicated to the people the news of the defeat in a public proclamation on 4 March 1811 :