The meaning of the term has evolved with the history of civilization. In the earliest times an enemy was a person with whom one was not connected by ties of blood. This also applies under some modern social extremes, as within urban gangs who symbolize their kinship with blood oaths. Similarly all foreign states were then regarded as enemies. The utmost cruelty was justified towards such enemies. At present an individual is not necessarily accounted the enemy of the state with which the government to which he owes allegiance is at war. But an individual may acquire enemy character because of his acts during wartime. In addition to personal enemies, enemies are now engendered by class warfare (class enemies), trade wars, commercial competition and competing ideologies (ideological enemies).
Friends come and go, but enemies accumulate.
Man does not live by bread alone, but also by the nourishment of animosities.