The capture of the frigate Esmeralda was a naval operation conducted on the nights of 5 and 6 November 1820. A division of boats with sailors and marines of the First Chilean Navy Squadron, commanded by Thomas Cochrane, stealthily advanced towards Callao and captured the ship through a boarding attack. was the flagship of Spanish fleet and the main objective of the operation. She was protected by a strong military defense that the royalists had organized in the port.
Both Chilean and Spanish historiography considers that as a result of this naval action the importance or maritime influence of the Spanish Navy in the Pacific disappeared completely. British historians Brian Vale and David J. Cubitt follow the same line of opinion when affirming that Spain had unquestionably lost control of the sea against the Chilean Navy.
Background
On 20 August 1820, the Liberating Expedition commanded by General José de San Martín sailed from Valparaíso to Peru. This force was escorted by the Chilean fleet, under the command of Vice Admiral Cochrane.
From the beginning of the campaign, San Martín and Cochrane had differences regarding the military strategy that they should carry out in Peru. The first wanted to avoid direct fighting, win over the population and press with indirect actions toward Lima. The second wanted to give a decisive blow to the royalists with both army and navy. San Martín's line of thought prevailed.
The expeditionary force arrived on 7 September in Paracas, near Pisco. San Martin established his headquarters to put pressure on the royalists. The Viceroy Juaquin de la Pezuela entered into negotiations with San Martin, based on the new political situation in the Iberian Peninsula with the proclamation of the Spanish Constitution of 1812. However, the negotiations that took place between the end of September and the beginning of October did not prosper.
At the beginning of October, San Martin sent a division of the army to the Peruvian highlands to revolutionize the territory, giving the command of this force to General Juan Antonio Álvarez de Arenales.
On 9 October 1820, the garrison of Guayaquil mutinied and proclaimed the independence of the city. This event had material and moral consequences in favor of the revolutionary cause in Peru.
On 26 October, the expeditionary force left Pisco to the north, arriving on the 29th in front of the Callao. The next day, San Martin went to Ancón with the purpose of executing military operations on land. For his part, Cochrane occupied the island of San Lorenzo and stayed at the port's approaches to establish a rigorous blockade with several ships.
Blockade of Callao
Inactivity of the Spanish Navy
Since the arrival in September of the liberating expedition to the Peruvian coast, the Spanish Navy had not accomplished any effective actions to repel or at least harass the revolutionaries, granting them control of the sea. This was due to the inflexible defensive policy of the Viceroy Pezuela, and the incompetence of the Commanding General of Navy Antonio Vacaro.
The Spanish fleet, based in Callao, was mainly formed by the frigates Prueba, Venganza and Esmeralda, together with several other armed ships. The first two frigates, commanded by Captain José Villegas, left the port on 10 October to the Peruvian south with the purpose of embarking troops, leaving the third frigate and the other ships under the impressive defense of the port, constituting a floating palisade that was protected with gunboats and batteries. Vacaro made this third naval unit the flagship of the squadron under his command.
This was the situation of the Spanish fleet at the time when Cochrane had established the blockade of Callao on 30 October, having at his disposal the frigates and , and the corvette .
The Cochrane plan
The blockade was maintained without difficulty by the Chilean fleet, since the Spanish fleet remained entirely on the defensive. However, this inactivity, made Cochrane impatient, and led him to undertake naval action.
To break the monotony of the blockade, he planned to inflict a great blow on the royalists in their strong defenses, similar to the capture of the defensive system of Valdivia. On the basis of his own information and that of a subordinate, he decided to undertake a surprise assault, entering the port at night with several boats and seizing the Esmeralda by means of a boarding attack. As a complement to this plan, he intended to capture or burn the other ships.