A hand lets go of the sword at the exact moment the standard behind it turns negotiable.
Weariness is a signal, and what it will mean is decided long before it arrives. To most of that army it meant the fighting was finished, which is why they were available afterward for plunder and not for the battle. To one man it carried no information about whether to continue, because continuing had been settled before his arm began to shake, and a settled question does not reopen under pain.
Yahweh worked the great victory through the man still on the field after the standard had thinned the ranks. Whoever keeps a quiet option to quit spends the hardest hour bargaining over whether to use it, and gives back ground already paid for.