The Army on the March · Discipline through Kindness and Severity
If soldiers are punished before they have grown attached to you, they will not prove submissive; and unless submissive, they will be practically useless. If, when the soldiers have become attached to you, punishments are not enforced, they will still be useless. Therefore soldiers must be treated in the first instance with humanity, but kept under control by means of iron discipline. This is a certain road to victory.
Punish soldiers before they trust you and they will not obey; win their trust and then fail to punish, and they cannot be used. Win them with kindness, then hold them together with discipline.