The First Horses in Mexico
Footing
Throughout the account, the ground the horses stood upon consistantly impacted their effectiveness.
Cortes, on account of the bogs which our horse could not pass, was obliged to take a circuitous route. (Diaz, 1568)
Good footing created a tremendous advantage for the cavalry, allowing the horses to be used at their most effective.
In one of these moments Cortes came galloping up with the horse. Our enemies being still busily engaged with us, did not immediately observe this, so that our cavalry easily dashed in among them from behind. The nature of the ground was quite favorable for its maneuvers; and as it consisted of strong active fellows, most of the horses being, moreover, powerful and fiery animals, our small body of cavalry in every way made the best use of their weapons. When we, who were already hotly engaged with the enemy, espied our cavalry, we fought with renewed energy, while the latter, by attacking them in the rear at the same time, now obliged them to face about. The Indians, who had never seen any horses before, could not think otherwise than that horse and rider were one body. Quite astounded at this to them so novel a sight, they quitted the plain and retreated to a rising ground. (Diaz, 1568)
Tactics and terrain needs frequently did not match. Plans were adjusted to suit the needs of the horses.
Cortes now related why he had not come sooner. First, he had been delayed by the morass; then again he was obliged to fight his way through other bodies of the enemy whom he had met, in which five men and eight horses were wounded. (Diaz, 1568)
As the ground here was full of deep cavities our cavalry were completely useless, until by using the greatest precaution they managed to pass over these. (Diaz, 1568)
Though the number of loose stones here were great obstacles to the cavalry (Diaz, 1568)
Quoting Cortez (Lockhart Trans):
It would be capital if we could gallop across these sand-hills at full speed; but, as we should so easily stick in the sand, it will be better for us to ride two and two along the sea-shore at low water. (Diaz, 1568)