The Battle of Tacna, also known as the Battle of the Halt of the Alliance (Spanish: Batalla del Alto de la Alianza), effectively destroyed the Peru-Bolivian alliance against Chile, forged by a secret treaty between both countries signed on 1873. On May 26 1880, the Chilean northern operations army led by General Manuel Baquedano Gonzalez, conclusively defeated a Peru-Bolivian army commanded by the Bolivian President General Narciso Campero, after almost five hours of fierce combat. This battle took place at the Intiorko hill plateau, a few miles north of the Peruvian city of Tacna. As a result of this battle, the Bolivian army returned to its country, and never participated in the conflict again, leaving Peru to fight the rest of the war by themselves . Also, this victory consolidated the Chilean domain over the Tarapacá Province, territory definitively annexed to Chile after the sign of the Tratado de Ancón (English: Treaty of Ancon), on 1884, which ended the war.
Accordingly to this purpose, and in order to isolate the two Allied strongholds in the Peruvian department, Arica and Iquique, from each other; the Chilean army launched an amphibious operation at Pisagua, on November 2, successfully pushing the Allies inland. This initial success was consolidated after the consecutive victories at Germania, on November 6, and the Battle of San Francisco or Dolores , on November 19. This chain of Chilean victories came to an end with the Peruvian victory at Tarapaca, on November 27, 1879. In this battle, a Chilean force of 2.000 men attacked recklessly an Allied army of 4.000 soldiers, suffering a heavy defeat.
The Chilean High Command planned a landing at Ilo and Pacocha in order to scout the country and to make an idea of the Allied army status. After two incursions, a main landing took place at Ilo, unshipping 10.000 men. After the resignation to the High Command of Gen. Erasmo Escala, due to the constant arguments with the War Minister Rafael Sotomayor, the Chilean Minister named General Manuel Baquedano, a veteran of the Peru-Bolivian Confederation war who had the sympathies and respect of the soldiers as Commander-in-Chief of the Operations Army. Since the beginning of the conflict, the infantry soldiers were equipped with Comblain rifles. The artillery had 37 cannons, between 20 Krupp cannons model and 17 mountain batteries.
Due to the scout mission success, a massive landing took place between February 18 and 25. 9.500 troops were disembarked in three divisions, whereas another one stood back at Pisagua, waiting for the convoy to return. On February 27, the Chilean Navy starts the bombardment of Arica. In this events died the Huáscar new captain, the Chilean Captain Manuel Thompson. On March 8, a Chilean armed expedition of 900 soldiers was sent to Mollendo, led by Colonel Orozimbo Barbosa. On the 18, Gen. Campero's 5th Division reached Tacna. On the 22, a battle took place at Los Ángeles hill, ending with a definitive victory of the Chilean Army, after the Chilean Atacama Bn. climbed the abrupt slope of the hill and caught the Peruvian troops from the rear. On April 9, the Peruvian port of El Callao is put under naval blockade. After the battle at Los Ángeles, the Chilean army started to march across the desert to Tacna. The artillery however, was embarked again and shipped to Ite, taking four days to unload these batteries. On May 20, War Minister Rafael Sotomayor died due to a stroke at Las Yaras. The Chilean President Anibal Pinto appointed José Francisco Vergara as the new War Minister in Campaign.
Whilst the Chilean Army evolved in the Tacna Department, the Allies had their own problems. Montero wanted to wait the Chilean troops at Tacna, but Col. Eliodoro Camacho supported the idea to march and ambush the Chileans at Sama river valley, easing the communications with Arequipa. Trying to avoid any confrontation, Gen. Campero traveled to Tacna to take charge of the Allied Army, assuming his command on April 19. On the night of May 25, Campero's troops tried to ambush the Chileans at Quebrada Honda, but the night and the mist prevented the Allies to do so, returning to Tacna for defense preparations. The next day, about 11.000 Chileans would fight against 10.000 Allies.
The Allied plan consisted in exploiting the terrain tactical advantages. The troops didn't entrenched, but just waited the Chilean Army deployed in a 3 km defensive line. On the far right were the Bolivian troops with 5 Krupp cannons, and the Murillo Battalion, followed by the Peruvian 1st Division commanded by Justo Pastor Dávila. At the line center, had been deployed the Bolivian Loa, Grau, Chorolque and Padilla battalions. Right next to this troops were the Caceres' and Suárez divisions. To the left of the previous units were 9 cannons and the Col. Luna's division. On the far left were the Bolivian Amarillos, Aroma and Colorados battalions. The right wing was under the command of Lizardo Montero, the center was led by Col. Castro Pinto, and the left flank by Col. Eliodoro Camacho.
Baquedano decided to use the plan of Velásquez. Thus, the army was split into five divisions, placing on the first line the 1st Division of Col. Santiago Amengual and the 2nd Division of Col. Francisco Barceló. Right behind them was Col. Orozimbo Barboza's 3rd Division. Col. José Amunátegui's 4th Division deployed on a third line, and behind this last one, the reserve.
The fight continued until 12:30, when the Chilean fire started to fade as ammunition ran out. Due to this, both divisions refolded, using their last bullets, chased by the Colorados, Zepita and Aroma battalions. The Allies began to counter-attack, advancing their left and center units, specially the ones on the left wing. The Chilean Atacama and Santiago regiments of the 2nd Division suffered heavy losses while retreating.
Furthermore, Col. Pedro Lagos, taking notice of the detain of the Allied offensive, asked Barboza's Division to reinforce the retiring divisions. The Coquimbo Battalion strengthened Barceló's troops, as the Chacabuco and Artillería de Marina regiments reinforced Amengual's Division. Once reinforced and resupplied with ammunition, both 1st and 2nd divisions advanced in guerrilla formation, making an intense fire upon the Allies and forcing their battalions to return to their initial positions. The Allied soldiers who couldn't return to their positions in time were surrounded and shot. The Chilean infantry continued their deployment until both armies were at close range, when the infantrymen drew their bayonets and corvos, engaging the Peruvian line. The Victoria Battalion gave under the thrust of this attack and withdrew, collapsing the defensive line, deciding the battle.
The Chilean Army lost 2,200 men between dead and wounded. The 1st, 2nd and 3rd divisions, which added up 6,500 men, had 1,639 casualties. Amunátegui's 4th Division lost 15% of its force. The Chilean reserve almost didn't fight, in fact, had only 17 wounded. The units Atacama and Santiago lost almost 50% of their effective force. Also the units 2nd Line, Naval and Valparaíso infantry regiments had severe losses. The 2nd Line Regiment estandard lost at the battle of Tarapacá was found on a church in Tacna by Ruperto Marchant Pereira.
The Allies had casualties estimated between 3,500 and 5,000 men. The Bolivian Army lost 23 officers from Major to General. The Colorados Bn. had only 293 survivors. The Sucre Bn. - also known as Amarillo - lost 388 soldiers, since these units chose to fight instead of retreat. The Peruvian army lost 185 officers, and died more than 3.000 soldiers. Accordingly to a relation of Solar to Piérola, only 400 Peruvian men escaped from the battle.
This victory had a decisive impact on the Allies. Gen. Campero withdrew to Bolivia taking the road to Palca. Montero retired to Puno, passing through Tarata. Bolivia would never participate in the conflict again, leaving its ally alone with no support whatsoever. Hence, Peru had to face the Chilean army alone for the rest of the war, receiving no help of any kind from his former ally.