After the Chilean navy obtained a decisive victory at
Angamos (October 8, 1879), the Chilean preparations for the invasion of the Tarapacá department began. On November 2, the Chileans launched an amphibious operation at
Pisagua and pushed the Allies offshore, and established a beach head to transport equipment and soldiers. Also, the loss of Pisagua deprived Gen. Buendía of the only available escape route he had left, because
Iquique was under blockade since the war broke out. Buendía was in fact in a very dangerous position. He was obliged to retake Pisagua at all cost to re-open his line of communications. If not, his only way out of Tarapacá would be marching to Arica through the
Atacama Desert. To make things worse, his troops were scattered all over the region. After defeated at
Pisagua, Buendía retreated to Iquique where he joined
Cáceres and Bustamante. Col.
Pastor Dávila never moved from Pozo Almonte and Gen.
Carlos de Villegas went to Puerto Patillo. Another two divisions were between Pozo Almonte and Iquique, while Villamil retreated to Agua Santa. The Aroma Battalion was at Mejillones and the Vengadores Battalion was at Agua Santa. When the news of the Chilean victory reached
Tacna, the Allies quickly held two war councils. In those, it was decided that Bolivian President General Hilarión Daza would drive his army to Tana, a few kilometers north of Pisagua, where he would join with Buendía and assume the command of the entire allied army. When reunited, Daza would attack Pisagua to regain the port. Two gunned trains transported Daza's troops and supplies to Arica, from where the march started on November 6. To reach the rendezvous point of Tana, the Bolivians should walk about 150 kilometres across the most arid desert on Earth. Therefore, President Prado advised Daza to march at night to keep troops' welfare. But what Prado didn't know was that Daza wasn't sure of his troops' loyalty, so he deliberately wore down his army. The men marched in daylight across the desert and were allowed to bring wine with them. When Daza reached Camarones, he had already lost 200 men. Using this as excuse, Daza retreated to Arica without meeting with Buendía. This is known until this day as the
Camarones Betrayal. When Buendía was notified of the battle plan decided at Tacna, he began to reunite his army. He left Iquique on November 5 with three battalions and moved north east, deep into the Tarapacá Department. Buendía spent almost two weeks gathering his divisions, completing his army only by the 16, when he reached Agua Santa. The Allies marched to Negreiros on November 17, then turned north to Porvenir. From there Buendía would march to encounter Daza at Tana, passing through Santa Catalina. At 3 pm on November 19, the allied vanguard saw the Chilean army occupying San Francisco Hill. On the Chilean side, right after Pisagua, Lt. Colonel José Francisco Vergara proposed an immediate reconnaissance for water supplies. With a cavalry detachment, Vergara rode on November 5 following the railroad to Dolores saltpeter office, finding the installations and water machines in good condition. The next day, the detachment resumed its mission, and in doing so annihilated two allied cavalry squadrons at Germania. Immediately, Sotomayor sent Col. Amunátegui with a regiment, two cavalry companies and one battery to Santa Catalina, about 6 kilometers south of Dolores. Two hours later, Col. Juan Martinez' Atacama Battalion was dispatched as reinforcement. Simultaneously, Col. Ricardo Castro was ordered to return from Jazpampa, where he was sent with 1,800 men to wait for Daza's army. Castro left in place the Bulnes Battalion and returned to Dolores with Velasquez' artillery. Both Castro and Velasquez arrived on the 19th, when the allied army was already deploying in front of Sotomayor. After his return from Tana, Lt. Col. Vergara spent great efforts in trying to convince Sotomayor to deploy the army over San Francisco Hill, instead of Santa Catalina. Vergara acknowledged the huge mistake Sotomayor was making, since the Chileans were outnumbered in a proportion of 2 to 3. The discussion became more and more violent between them, but finally about 1 am of November 19 Sotomayor gave and ordered Amunátegui to return from Santa Catalina. While at Santa Catalina, Amunátegui's cavalry captured three Argentinean scouts who informed that the whole allied army was coming from Agua Santa. At the same time, Buendía was marching to Santa Catalina, a little more west from Amunátegui's position. But, the reconnaissance of both sides was very defective and the enemies weren't aware of each other. Amunátegui reached Dolores at done of the 19, and the Allies arrived shortly after. Buendía's vanguard established around the water well at Porvenir, about 1.2 kilometers south of San Francisco Hill. == Armies layout ==