A blockade was originally a naval siege, which prevented ships from entering or leaving an area (172). Later, it was used to describe sealing off any type of area to prevent goods or people from entering and leaving. Walzer argues that it is morally permissible to block military supplies, but he objects to the expansion of blockades to economic warfare: Therefore, he considers the British blockade of the entire German coast in World War I unjust.

The term Demi-monde, meaning “half-world,” originated in 19th-century France. Its primary meaning is the realm of society populated by disreputable women. Walzer uses the term to refer to the period between wartime and peacetime. In such times, there can be border strife and periods of insurgency. Walzer explains that such times are commonplace and appropriate for peacetime reprisals.

Australian political theorist Headley Bull (1932-1985) coined the term domestic analogy. The domestic analogy assumes that a state operates like a society of individuals: Walzer notes its importance to the theory of aggression because any major international conflict threatens the world order, and there is no international police force. The domestic analogy defines as aggression any use of or imminent threat of force of one state against another (62).