Soldiers must be first treated in the first instance with humanity, but kept under control by means of iron discipline.
The Art of War is self-explanatory.
Danger has a bracing effect.
Thus, what is of supreme importance in war is to attack the enemy's strategy.
The art of war, then, is governed by five constant factors, to be taken into account in one's deliberations, when seeking to determine the conditions obtaining in the field.
If soldiers are punished before they have grown attached to you, they will not prove submissive; and, unless submissive, then will be practically useless. If, when the soldiers have become attached to you, punishments are not enforced, they will still be useless.