As soon as it was notified of the blockade of Iquique, the Peruvian naval command carried out its initial operations as planned.
The “Unión” and the gunboat “Pilcomayo” set sail from El Callao on April 8 to intercept Chilean maritime communication lines south of Iquique, in order to deny supplies to Chilean ships.
Admiral Juan Williams Rebolledo knew of this departure, but, believing it to be the monitor “Huáscar” with the gunboat “Pilcomayo” and fearing a bombing of the water treatment plant in Antofagasta, he ordered the departure of the armored ship “Cochrane” and the gunboat “Magallanes” to that port.
Meanwhile, the Government sent urgent telegraphed instructions to Admiral Williams in Antofagasta.
When the ships arrived at the port, the gunboat “Magallanes”, under the command of Commander Juan José Latorre Benavente, was commissioned to carry said communications to Iquique.
On the morning of April 12, already in the block of Chipana Point, he sighted the Peruvian ships “Unión” and “Pilcomayo”, which immediately steered to close the distance with the gunboat.
Both were superior to the gunboat “Magallanes” in speed and armament. At 10:50, the gunboat “Pilcomayo” opened fire at 3,550 meters, followed by the “Unión.”
Frigate Captain Juan José Latorre Benavente ordered the battle flag to be raised, with a loud “Viva Chile” from his crew. He decided not to return fire from the gunboat “Pilcomayo” to concentrate his limited weapons on the “Unión.” The third shot scored a hit, generating a massive burst of steam. The ship stopped momentarily and then turned, opening up the distance to rejoin the gunboat “Pilcomayo,” and both decided to end the action.
Commander Juan José Latorre Benavente arrived in Iquique, handed the document to the Admiral, and fully fulfilled the purpose of the commission.
The Peruvian ships failed to take advantage of their superior speed and armament to put the gunboat “Magallanes” between two fires.
The “Unión” had to return to El Callao for repairs, and the gunboat “Pilcomayo” to Ilo for coaling.
Frigate Captain Juan José Latorre correctly applied the principle of maintaining the target. Two ships engaged a weaker one and were repulsed with damage.