The battle was the culminating point of a naval campaign that lasted about five months in which the Chilean Navy had the sole mission of eliminating its Peruvian counterpart.

In the struggle, two armored frigates, led by Commodore Galvarino Riveros Cárdenas and Navy Captain Juan José Latorre battered and later captured the Peruvian monitor Huáscar, under Rear Admiral Miguel Grau Seminario.

After the loss of the frigate Independencia at Punta Gruesa, Grau sought to challenge the outnumbering Chilean fleet with a harassing strategy, focused on inflicting as much damage as possible while avoiding a full-scale engagement.

Falling in a trap set by Riveros and Latorre, Grau was forced to present battle after ordering the corvette Unión to escape to Perú.

Chilean Navy dominance off the Pacific coast contributed significantly to success in the following land campaigns across the Atacama Desert that ended with Lima's fall in January 1881.

This obliged Rear Admiral Miguel Grau to renounce to attack and to adopt a harassing strategy, avoiding by all means a direct encounter with the bulk of the Chilean navy.

Aboard the monitor Huáscar, Grau made several incursions into Chilean waters, successfully challenging the enemy's domination along the coast.

By 30 September, Riveros was notified that the corvette Unión was sailing to Panamá to escort five small ships with torpedoes bought from the United States.

[2] In a council held aboard Riveros' flagship, the armored frigate Blanco Encalada, it was decided to set course to Arica, hoping to find Huáscar there.

So, the fleet was divided as it follows: On 1 October, Riveros gathered his officers and communicated the order of hunting down the Peruvian vessel at Arica.

Since the Chilean fleet sailed close to the shore and the Peruvians were farther out in the open sea, both formations didn't spot each other.

Riveros' division would wait for Grau at Antofagasta while Latorre would set up an east–west barrier-like formation about twenty miles (32 km) from shore.

Riveros ordered a speed reduction of his to make Grau think it was possible to turn back north and sail for Perú.

[5] Grau's flagship listed hard to starboard and was hampered also by a deformation in the hull acquired when she rammed Prat's Esmeralda at Iquique five months ago.

Lt. Captain Gaona's gunners caused heavy casualties among the Peruvian crew: the Chileans were using Palliser type armor-piercing rounds, which exploded right after penetrating the hull.

At 10:54 hrs the order was given to evacuate the wounded from the engine room and open the main condensator to scuttle the ship and to prevent its capture.

With Huáscar's capture, plus the previous loss of Independencia at Punta Gruesa, the firepower of the Peruvian Navy was drastically reduced, and Chile incorporated the monitor in its fleet.

The decisive victory at Angamos allowed the Chilean Army to freely pursue the plan to attack the Allies, and the land invasion of Peru began.