Except from the wars against the Muslims to rule the Iberian Peninsula, Alanos were used in the conquest of the New World. This process has a particularly well described course of wars and the subsequent stages of ruling America.
The monastic chroniclers accompanying armies were meticulously describing course of events. Thanks to them, the military actions of those times are known precisely nowadays. The annalist Lopez Gomara had reported that 200 soldiers, 20 horses and 20 dogs had been used by the Spanish against the native Americans under commands of Caonabo chief in an important battle for the Antilles on March 24 1495. Alanos were used not only during the first attempts of colonizing the New World. They were fighting by the conquistadors in Venezuela, Mexico, Peru, Argentina and Chile, where they played an important role in the Arauco battle.
The aforementioned Lopez Gomara describes a series of battles with fighting dogs; one can find quite precise description of the dogs that were spreading terror among the native Americans. "Their dogs are enormous, they have waving flat ears, big hanging tongues, small yellow eyes sight of which freezes blood in veins. They are very strong and muscled, they aren't still, they walk wheezing loudly with hanging tongues, their fur looks like jaguar". Very pertinent description of Alano. Carlos Contera in his work "El Perro en la Conquista de las Indias" points out, that the dogs in the New World didn't have cut ears because of the climate - to avoid infections and improve thermal regulation.
Alanos were terrorizing American warriors which have never seen dogs like these before. Before the European Conquest Americans didn't know horses and their dogs were small and fearful.
Gomara gives an example of the reaction of Americans to the dogs in a description of a battle in 1510. The governor Vasco Nuez de Balboa, meeting with the Indian chef Chapie, was forced by him to fight, as the Indians had estimated their chances if fighting the Spanish as high. In response, Balboa let out his dogs, that fearlessly attacked the opponents, forcing them to run away into the fire line prepared by the Spanish. Alano was usually used with the cavalry, which was a powerful combination. It was its efficiency and look that caused the Americans to call Alano "the devil's invention". A common picture during fights were the Indians running away after letting Alanos out. The dogs running at a front of Spanish soldiers were terrorizing Indians with their "wild, blood-freezing sight and weird barking".
The dogs were an invariant element of conquistadors' journeys and together with four riders they were forming the army's outpost. This configuration is known from the descriptions of Herman Cortes' journeys.