Their arms were weary with striking.

The sun blazed down upon them with scorching heat.
Their throats were parched with thirst.

They were enfeebled by hunger.
The Aztecs, seeing that their foes were becoming faint and wearied, that the horses of the cavaliers could scarce carry them, and that the end was approaching, redoubled their shouts; and pressed more heartily and eagerly than ever upon the Spaniards, driving the cavalry back, by sheer weight, into the ranks of the infantry.
Cortez, at this supreme moment, still maintained his calmness.

He saw that all was lost, unless a change was made, and that speedily.
Another hour at latest, and the resistance would be over, and the brave men who had followed him be either dead, or prisoners reserved for sacrifice.
Throughout the day he had ordered his cavaliers to strike ever at the chiefs, knowing well that undisciplined bodies of men become lost, without leaders.

Raising himself in his stirrups, he looked round over the seething mass of the foe; and at some distance beheld a small body of officers, whose gay and glittering attire showed them to belong to the highest rank of nobles; gathered round a litter on which was a chief, gorgeously attired with a lofty plume of feathers floating above his head; rising above which was a short staff, bearing a golden net.
Cortez knew that this was the symbol carried by the Aztec commanders in chief.