The South American War was an armed conflict lasting from 1916 to 1928 on the continent of South America. It was fought between the Brazilian Alliance, led by the Empire of Brazil, and the Argentine Alliance, led by Argentina. It was the successor of the Atacama War, with the alliances staying the same. It is also known as the Forgotten War, due to being overshadowed by the Third Great European War and the Second Pacific War. When it is grouped with those two other wars, it is known as the South American Theater of the First Great War.
Peruvian and Bolivian troopers soon began to march into the former Bolivian coast, which was taken from them by Chile. Their goal was to take Tacna, the Chilean base of operations and a major city in Atacama region. When word of the attack reach Santiago, soldiers were hurriedly sent to protect the vital city. A ring of trenches were dug around the city as a defensive line against the Peruvians and Bolivians. The marching Peruvians and Bolivians were fired upon by the Chilean machine guns. They were forced to find cover, and dug small holes in the ground. The Peruvian commander, Augusto B. Leguia, ordered his soldiers to connect these holes, forming their own trenches. The two sides were locked in a stalemate, and several attempts to cross from one side to another was violently broken up with machine guns.
Argentina begin to send its military into the Andes Mountains, hoping to eventually cross into Chile. Chile had reinforced their bases in these mountains for the past decade, and were quite strong. The Chileans had brought over many Brazilian and American weapons, giving them a slight advantage over Argentina. The Argentines entered the mountain range in June under the command of Marcelo Torcuato de Alvear, and were blasted by Chilean artillery. The Argentines responded with their artillery barrages. The attack was heaviest in the center of the Argentina-Chile border, the Argentines had attempted to cross many of the passes. One of the most hotly contested ones was the Carirrine Pass. The fighting their lasted twenty days until the bloodied Argentine forces retreated.
Meanwhile, Chile's allies in South America, Brazil and Venezuela, came to their rescue. Brazil began launching attacks into northern and eastern Argentina, but the Argentines, expecting a Brazilian attack, had heavily fortified the regions. Venezuelan troops were sailed from port cities in Venezuela to Montevideo, where they sent to the battle front.