BAP Unión was a corvette of the Peruvian Navy, originally ordered by the government of the Confederate States of America during the American Civil War.

During the American Civil War, the Confederate States ordered the French shipbuilder Henri Arman de Rivière to build 4 cruisers.

When the Union corvette arrived in England from France to enlist a crew, on 17 January 1865, its commander Grau was arrested at Plymouth, accused of having violated the principles of neutrality that the port imposed on all foreign warships.

Federico Barreda's energetic protest before Count Russel managed to annul the arrest warrant against Grau, and the Union and its twin America were able to continue their trip to Peru.

When the convoy managed to get ready to sail, it was again surprised at less than one hundred miles off the Brazilian coast by a furious gale that damaged the Union's trees, which re-entered the port of Rio de Janeiro towed by America.

On 5 December 1865, the new Peruvian government headed by Colonel Mariano Ignacio Prado signed a treaty of alliance with Chile as a prevention of an imminent war with Spain.

A Naval Division was formed under the orders of Captain Manuel Villar Olivera, made up of the frigates Amazonas and Apurímac and the corvettesUnión and América, which marched to Chile.

On 16 January, the frigate Amazonas sank off the extreme southwest point of Abtao Island, in Chayahué, where the allied squadron was stationed.

Union participated together with the Peruvian squadron and the Chilean gunboat Covadonga in the Battle of Abtao against the Spanish screw frigates Reina Blanca and Villa de Madrid.

In April, the Union and America set sail for the Strait of Magellan to look for the new Peruvian armored ships, but returned without finding them, as they were still on the way.

The Union was sent in May to Valparaíso to pick up Vice Admiral Manuel Blanco Encalada to take command of the allied squad, but upon leaving Huito, the Chileans fired the cannons on the beach, which had belonged to the Peruvian frigate Amazonas, fulfilling Williams's old order not to let the Union leave, an order that it had not been canceled.

On 6 June 1866, the allied squad finally joined the new armored ships frigate Indenpendencia and monitor Huáscar, in Ancud, marching together to Valparaíso five days later.

The corvette was of return to Peru 11 July 1873, after a trip of 94 days of which it spent a total of 16 in the ports of Plymouth, San Vicente, Montevideo and hours in Cabo Vírgenes, Posesión; Punta Arenas, Playa Parda, Puerto Angosto, etc.

In the early hours of the 20th, off Chañaral, the brig Saucy Jack, loaded with copper, fell into the hands of the Peruvian ships and sent to Callao.

Through papers obtained in the Rímac, the Peruvian command learned that the Gleneg steamer was carrying an important load of weapons for Chile: 4 thousand Gras rifles, 16 Krupp cannons and ammunition.

On 13 August, running a strong storm from the north, the Union sighted the strait and entered it at 3:30 pm, when it was already dark, so they kept to the layer between Westminster Hill and Cape Packer.

The Chileans also took away the heavy caliber cannons that defended the mouth of the port, artillery that had been mounted years ago, when the presence of the Argentine squadron was feared.

It was unknown in Punta Arenas that those days the Genovese steamship was supposed to arrive with another important shipment of weapons for Chile.

The Union and the Huáscar traveled to Callao to escort the steamer Rímac, which was supposed to carry an important war cargo to southern Peru.

The Rímac left some war supplies in Arica, at the same time that President Prado and Grau discussed a new incursion into Chilean ports; Grau suggested that the Union and Huáscar should return to Callao to maintain their ships, but as this would take a month, Prado insisted on an expedition further south, after which they would go to Callao before 15 October.

On 30 September 1879, the convoy left Arica and arrived in Iquique the same day, landing in that port the troops of the Explorer Division (1500 men) of General Bustamante.

In Sarco, the Peruvian ships seized and sent the Coquimbo sailboat to Callao and then continued, believing not to be seen, to the anchorage of this name (where an English and an American warship was) and reached Tongoi, beyond the parallel 30 °, already close to Valparaíso.

By allowing Grau to withdraw from the Union, all he did was adhere to the instructions given by the War Director, President Mariano Ignacio Prado, dated 30 September in Arica, in which article 7 read: "In no case will rear-admiral Grau compromise any of the ships under his command and if he encounters enemy ships in transit, he will only fight with lower forces, unless he is unable to retreat from superior forces, in which circumstances he will fulfill his duty."

The new government of Peru, represented by Nicolás de Piérola as Dictator, gave command of Unión to Captain Manuel Villavicencio.

In the early morning of 17 March, the Union, sheltered in darkness and absolute silence on board, entered Arica, sailing recklessly close to the coast and outwitting the blocking squad, which was at sea.

The Chilean ships Cochrane and the Amazonas joined the Huáscar and they opened fire on the Peruvian corvette and also on the monitor Manco Cápac until after 2 pm.

Finally, on 16 January 1881, the Union and other ships of the Peruvian Navy were sunk in Callao to prevent them from falling into Chilean hands, after the Lima Campaign ended .