Answer:
It appears that the Spaniards (the ones on the horses) have/almost defeated the Aztecs in a conflict.
Step-by-step explanation:
Several clues help come to this conclusion;
1. Notice how some of the Aztecans seem to be turning away from the Spaniards, or in other words, fleeing.
2. There is a amputated/injured Aztecan body on the ground.
3. In the far background, you can see that there's a limp body that's hanging; based off the earlier clues we have, we can infer that it's perhaps a Aztecan.
Hope this helps!