During an expedition over the conflicting seas, the Peruvian Navy ships, Huáscar and Unión, apprehend the Chilean war steamer Rímac, which was an artillery transport, taking all its cargo and capturing its crew, including a squad of the Carabineros de Yungay [es].

In Chile, the news of the capture of the Rímac detonated a political and social crisis that led to the resignation of several government officials, including Rear Admiral Juan Williams Rebolledo, Commander General of the Chilean Navy.

They also had newspapers that indicated in detail the movements of the squadron, these were supplied by friendly ships, in this way Grau knew that an important supplier was approaching Antofagasta.

The Copiapó, Toltén, Rímac and Package de Maule transports were about to arrive in Antofagasta with reinforcements for the Chilean army stationed there because it was getting ready for an early invasion of Tarapacá.

The Copiapó arrived in Coquimbo on July 19, but she immediately returned to Valparaíso along with the steamship Toltén and the corvette Chacabuco, due to telegrams that the Peruvian ships Huáscar and Unión were in Mejillones.

Santa María ordered the captain of the ship Enrique Simpson, commander of the Almirante Cochrane, to take coal to Tocopilla for the production of water for the population and the 500 mules gathered for the Tarapacá campaign, and to return on the 22nd to go south to meet the Rímac and the Maule.

Santa María ordered that the Lamar, with the deputy Máximo R. Lira, inform the Almirante Cochrane and the Itata that the transports would no longer arrive and travel to Caldera, where the telegraph reported the presence of the Huáscar and the Unión.

The frigate captain Ignacio Luis Gana was traveling on the steamer as a passenger, and he could take command of the ship only when the enemy was on top.

Recognizing the Peruvian corvette 4 miles away, Lautrup relinquished command to Gana, in accordance with his contract, changed course first and tried to take cover.

The sailors of the Rímac, mostly foreigners, rushed to the canteen wanting to break down the door, but the Carabineros de Yungay [es] intervened to impose order.

At 8:45 on board the Rímac, the council of officers met to determine the possibility of throwing the heaviest weapons off the ship along with the horses, the latter being prevented by the carabinieri squad given the esteem that they had him.

2nd Lieutenant Felipe La Torre Bueno was in charge of "taking possession of the ship in the name of Peru and sending it to his commander and flag on board."

Then the Huáscar stood alongside the Rímac and Grau appointed the graduate frigate captain Melitón Carvajal as provisional commander.

Commander Pedro Lautrup, Lieutenant Colonel Manuel Bulnes, and 25 other prisoners were transferred to the Huáscar; the frigate captain Ignacio Luis Gana and 55 other crew members, to the Union .

1 cavalry squadron with 258 men, 215 horses, 1 300- pound cannon, 300 Comblain II rifles with 200,000 shots, some Winchester carbines, ammunition, provisions, coal, fodder were captured in the transport, supplies for the ambulance, money and official correspondence.

On July 24, Santa María received the news of the arrival of the ironclad Almirante Cochrane to Caldera towed by the Itata transport due to lack of coal.

In the interpellation session, the entire cabinet came out well, but the Minister of War and Navy, General Belisario Urrutia, who was offended by Vicuña Mackenna within the Chilean Senate, resigned his portfolio on August 2.