The concept of an “act of war” has evolved significantly in international law, shaped by changing legal frameworks, political realities and the decline of formal war declarations. This analysis traces its historical trajectory and explores how Pakistan can safeguard its strategic interests while adhering to international legal principles.

In ancient civilizations such as Greece, Rome and China, warfare was guided by customs rather than codified laws. The Roman concept of bellum justum (just war) required both a formal declaration and moral justification. During the Middle Ages, issuing formal declarations became a key marker of lawful warfare. Legal scholars like Hugo Grotius later developed these ideas into a coherent doctrine, establishing that a declaration of war suspended peacetime obligations and triggered a distinct legal regime—the law of war.

This framework eroded after the World Wars of the 20th century. The 1945 UN Charter fundamentally altered the legal landscape, prohibiting the use of force under Article 2(4) and recognizing only two exceptions: the inherent right of self-defence and Security Council-authorized enforcement under Chapter VII. In this post-Charter era, states have moved away from formal war declarations, instead framing military actions as “self-defence,” “armed attack,” or “countermeasures.” Consequently, the term “act of war,” while influential........

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