Indian auxiliaries

Auxiliary Indians or indios auxiliares is the term used in old Spanish chronicles and historical texts for the indigenous peoples who were integrated into the armies of the Spanish conquerors with the purpose of supporting their advance and combat operations during the Conquest of America. They acted as guides, translators, or porters and in this role were also called Yanaconas, particularly within the old Inca Empire and Chile. The term was also used for formations composed of indigenous warriors or Indios amigos (friendly Indians), which they used for reconnaissance, combat, and as reserve in battle. The auxiliary Indians remained in use after the conquest, during some revolts, in border zones and permanent military areas, as in Chile in the Arauco War.

History
The formations of auxiliary Indians arose commonly from alliances established by the Spaniards, exploiting ethnic and tribal antagonisms that they found during their occupation of the territory they were attempting to conquer. Hernán Cortés was one of the first captains who was known to strengthen his columns with these natives. Commonly after the conquest these auxiliary Indians were divided among the settlers of the territories already conquered. They often constituted the most numerous group of the conquerors' followers:

Guatemala
The expedition of Pedro de Alvarado to Guatemala was composed of 480 Spaniards and thousands of auxiliary Indians from Tlaxcala, Cholula and other cities in central Mexico. In Guatemala the Spanish routinely fielded indigenous allies; at first these were Nahua brought from the recently conquered Mexico, later they also included Maya. It is estimated that for every Spaniard on the field of battle, there were at least 10 native auxiliaries. Sometimes there were as many as 30 indigenous warriors for every Spaniard, and it was the participation of these Mesoamerican allies that was particularly decisive. Some newly conquered Maya groups remained loyal to the Spanish once they had submitted to the conquest, such as the Tz'utujil and the K'iche' of Quetzaltenango, and provided them with warriors to assist further conquest.

In 1524, fresh from his victory over the Tz'utujil, Pedro de Alvarado led his army against the non-Maya Xinca of the Guatemalan Pacific lowlands. At this point Alvarado's force consisted of 250 Spanish infantry accompanied by 6,000 indigenous allies, mostly Kaqchikel and Cholutec.

The Mam fortress of Zaculeu was attacked by Gonzalo de Alvarado y Contreras, brother of Pedro de Alvarado, in 1525, with 40 Spanish cavalry and 80 Spanish infantry, and some 2,000 Mexican and K'iche' allies. When the Spanish besieged the Ixil city of Nebaj in 1530, their indigenous allies managed to scale the walls, penetrate the stronghold and set it on fire. Many defending Ixil warriors withdrew to fight the fire, which allowed the Spanish to storm the entrance and break the defences.

Perú and Chile

 * During the siege of Cuzco, Francisco Pizarro had 200 Spaniards and 30,000 native Huancas, Cañaris and Chachapoyas.
 * The column of Diego de Almagro, who went into Chile, had 500 Spaniards, 100 African slaves and about 10,000 auxiliary Indians.
 * In the case of the conquest of Chile by Pedro de Valdivia, the original group who left Cuzco included 11 Spaniards and 1,000 auxiliary Indians.