The armies fought all day without a decisive victory, then ceased fighting at night to retire to their respective camps. This observance of the day’s end is quite typical of battles among the later Aztecs.
The howlings and lamentations (v. 16) are an authentic part of Ether’s record—not only faithfully reflecting the survivors’ sorrow but also a dramatic part of Ether’s perceptions from his distant location. He might not have been able to identify specific clashes or identify the slaying of specific individuals; but in the night stillness, these sounds of mourning would be particularly poignant.