The law of war, a foundational element of international law, governs the conditions for engaging in conflict (jus ad bellum) and the moral conduct during hostilities (jus in bello), covering topics ranging from sovereignty to banned weapons. With roots in historical documents such as the Code of Hammurabi and religious teachings, it has developed through agreements like the Hague Conventions and Geneva Accords.
Thinkers such as Francis Lieber stressed restrictions on cruelty and violations of peacetime accords, while L. Oppenheim emphasized general principles that apply to combatants irrespective of the justification for war. The U.S. Congress outlined the legal basis for declaring war, illustrating the tension between state authority and humanitarian limitations. Collectively, these viewpoints demonstrate a complex relationship between national interests and the persistent goal of reducing the human cost of war.