" Declaration of war with Peru imminent Godoy and Lavalle will retire tomorrow. Proceed like in campaign. Godoy says to me: Situation Peruvian squadron in Callao is bad. To attack it by surprise at dawn would be safe but preferable to attack it outside the reach of our batteries. Peruvian army consists of 6,080 men. Two thousand five hundred policemen".

Shortly after it sent a new message:

"Declaration of war already known in Lima. You should try to destroy or to disabled the Peruvian fleet, prevent the fortification of Iquique or destroy it, apprehend transport and/or, block ports...”

Nevertheless, the Chilean naval command, instead of taking advantage of its powerful ships to attack the Peruvian fleet anchored in Callao, limited itself to bombard the southern ports of Peru. It also imposed a blockade on Iquique, which was the closest Peruvian port to Chile.

On April 12th, the first naval engagement of the war took place between the Peruvian corvettes Union and Pilcomayo with the Chilean corvette Magallanes. The so-called “Battle of Chipana” ended indecisively; nevertheless the Magellan had to escape to avoid her capture.

Admiral Williams’s strategic mistake would cost him dearly. On May 16, when he finally decided to attack Callao, the Peruvian First Naval Division, composed of the Huascar, the Independence and the transports Chalaco, Limeña and Oroya, plus the monitor Manco Capac had weighed anchors for Arica, escorting President Prado and the Chiefs of Staff.

At Arica, the Peruvians received news that the main Chilean fleet was navigating toward Callao and that three of its ships, the wooden corvette Esmeralda, the schooner Covadonga and the transport Lamar remained blockading Iquique. They also knew that an enemy convoy was transporting 2,500 soldiers from Valparaiso toward Antofagasta.

The situation required an immediate action, reason for which the Peruvian President ordered the Huascar and the Independence to head towards Iquique to break the blockade and to capture or destroy the enemy ships. Next they should to attack the convoy from Valparaiso and, finally, sabotage the schemes of water filtration at Antofagasta to avoid its use by the opposing troops.

At eight in the morning of May 21st, both Peruvian ironclads reached their objective and immediately approached to demand the surrender of the Chilean ships located at the entrance of the bay. Nevertheless of their inferiority, the Chileans refused to surrender and prepared to give combat. Understanding that there was no other option than to solve the situation by force, Commander Grau addressed his crew:

"Men of the Huascar. The time has arrived to punish the enemies of our homeland and I hope that you will bring new laurels and glory that could shine beside those of Junin, Ayacucho, Abtao and Dos de Mayo. Viva el Peru!"

The harangue of the Chilean commander aboard the Esmeralda was no less emotive:

“Boys, the odds are against us. Our flag has never been lowered in the presence of the enemy. I hope that will not be today. As long as I live that flag shall fly in its place, and, if I die, my officers will know how to do their duty”

The Peruvian ironclad was placed at a short distance and proceeded to discharge her guns. During the first thirty minutes she engaged alone with the two enemy warships. At the beginning the battle was fought at ranges between 800 to 2000 meters but little was accomplished. When the Independence, under Captain Juan Guillermo Moore approached to engage in combat, the Covadonga, under Lieutenant Carlos Condell, began to move away from the scenario heading for the South. It seems that Condell realized that he could escape by rounding the island at the mouth of the bay. Immediately Grau ordered Moore to pursue the schooner.

The Esmeralda was commanded by the brave Captain Arturo Prat and had a crew of 200 men, similar number to the endowment of the Huascar.

The corvette remained motionless but active; from her tops, rigging, and decks a steady rifle fire was maintained. So strong was the fusillade that the Peruvians thought it was coming from machine guns. However, the projectiles of the corvette were unable to pierce the armor of the Huascar, which in turn was forced to limit the use of her artillery fearing that her projectiles could reach the population of Iquique. However, at about 10:30 hours, a shell from the Huascar hit the corvette in one of her vital parts (engine room) killing all of the ship’s engineers. Grau then decided to finish the encounter by using the ram, but the first two intents were vain. The first one impacted to port and the second in the starboard of the Chilean ship, which did not surrender in spite of the heavy punishment she was receiving.

At the climax of the fight, the valiant Captain Prat tried to board the Huascar and accompanied only by a sergeant, sword in hand he hurtled over the ironclad, shot to death an officer and was killed on the deck after he tried to advance towards the bridge. A second boarding attempt by twelve crewmen under Lieutenant Serrano was also fruitless and most of them were killed. The Peruvians kept firing their guns before and after those collisions and the carnage on board the Esmeralda was appalling. By the second ramming, half of the Chilean crew had been killed.

Only at the third ramming, preceded by the impact of two 300-pound shells, the Esmeralda broke in half and collapsed with her mast on top. The dramatic combat, which lasted more than three hours, concluded at 12:10 noon and the Peruvian fleet had won its first victory in the war. In total Huascar fired forty gunshots. She lost one officer –Lieutenant Velarde- and had seven sailors wounded. The Chileans had 135 dead and dozens of wounded. Immediately the gallant Grau, before advancing toward the Covadonga, ordered the rescue of the 62 valiant survivors of the Esmeralda, whose last commander, Lieutenant Uribe, thanked the humanitarian gesture of the skipper of Huascar.

The Peruvian victory however was shadowed when the Independence, after closing to the Covadonga, tried to ram her at a place called Punta Gruesa. During almost three hours of pursuit Commander Moore had tried to destroy the Chilean vessel with his ship’s guns, but the fire was inaccurate. So he decided to ram her. He did it in two opportunities. The Covadonga was placed very near to the coast and the heavier Independence, while trying to perform this maneuver for the third time, collided with a submerged rock. Immediately the ironclad started to sink. Lieutenant Condell took advantage of the situation and fired at the Peruvian ship killing and injuring 26 of her crew. Among the death was Lieutenant Guillermo Garcia y Garcia, brother of the Commander of the Peruvian Second Naval Division. This way Peru lost a two thousand tons ironclad while trying to capture an old 412-ton schooner. Being or not registered the rock on the navigation charts, Captain Moore had made an unforgivable mistake that he would only redeem during his brave participation, eight months later, as commanding officer of the Arica batteries, during the battle of the same name.

Since that moment, Grau and the Huascar remained alone to face the almost intact Chilean fleet. Both, ship and commander would become the last obstacle that would prevent the Chilean forces to control the seas and to begin the land campaigns against Peru.