In 'Henry V' (either the old Olivier version or the 1989 Branagh version) there is a part where the king gives this 'commander's intent' to his troops when explaining his decision to punish a soldier caught looting:

"...we give express charge that in our marches through the country there be nothing compell'd from the villages; nothing taken but paid for; none of the French upbraided or abus'd in disdainful language; for when lenity and cruelty play for a kingdom, the gentler gamester is the soonest winner."