The most accurate response is:
Spaniards used horses to intimidate their opponents and demonstrate superiority and dominance in battle.
Horses provided the Spaniards with a significant tactical advantage during their conquests of the Aztec and Inca empires. The sight of mounted soldiers was unfamiliar to indigenous populations and contributed to the psychological warfare aspect of the conquests, as the horses were often perceived as fearsome and a sign of the Spaniards' advanced technology.