In this Aztec account the tall ''deer'' that carried the Spaniards on their backs were?

In the Aztec account, the tall "deer" that carried the Spaniards on their backs refer to horses. The Aztecs, unfamiliar with horses, likened them to large deer due to their size and the way they moved. The arrival of the Spaniards on horseback had a significant psychological impact on the Aztecs, contributing to the confusion and fear during the initial encounters.