The concept of "aggressor" originates in international law, signifying a party that initiates unlawful violence or conflict. Authors like Benjamin R. Tucker view aggression as a pathological act, while William Dean Howells examines its moral ambiguity in cases of justified retaliation.
Joseph Francis Delany and Carl Schurz highlight the importance of self-defense against unjust violence, distinguishing it from deliberate harm. Bahá'u'lláh emphasizes the duty to restrain oppressors, connecting aggression to systemic injustice. These viewpoints reveal the term’s dual function as both a legal label and a moral indicator, reflecting the tensions between violence, justice, and responsibility.