The natural principle of war is to do the most harm to our enemy with the least harm to ourselves and this of course is to be effected by stratagem.

Irving frames war as governed by a cold calculus: the “natural principle” is maximizing damage to the opponent while minimizing one’s own losses. From that premise, “stratagem” (deception, maneuver, surprise, intelligence, and indirect methods) becomes not merely permissible but the logical instrument of efficient warfare. The statement implicitly contrasts brute force with cunning, suggesting that the most “rational” conduct of war relies on planning and guile rather than sheer violence. Read more broadly, it reflects a realist view of conflict in which moral considerations are subordinated to outcomes and self-preservation, and where success is measured by asymmetry—achieving decisive effects at minimal cost.