Laws of war in the context of "Declaration of war"

The Hague Conventions of 1899 and 1907 are a series of international treaties and declarations negotiated at two international peace conferences at The Hague in the Netherlands. Along with the Geneva Conventions, the Hague Conventions were among the first formal statements of the laws of war and war crimes in the body of secular international law. A third conference was planned for 1914 and later rescheduled for 1915, but it did not take place because of the start of World War I.

Proportionality is a general principle in law which covers several separate (although related) concepts:

• The concept of proportionality is used as a criterion of fairness and justice in statutory interpretation processes, especially in constitutional law, as a logical method intended to assist in discerning the correct balance between the restriction imposed by a corrective measure and the severity of the nature of the prohibited act.
• Within criminal law, the concept is used to convey the idea that the punishment of an offender should fit the crime.
• Under international humanitarian law governing the legal use of force in an armed conflict, proportionality and distinction are important factors in assessing military necessity.
• Under the United Kingdom's Civil Procedure Rules, costs must be "proportionately and reasonably incurred", or "proportionate and reasonable in amount", if they are to form part of a court ruling on costs.

The principle of proportionality means that belligerents must not launch an attack when the anticipated death and injury to civilians is clearly excessive in light of the military advantage expected from the attack.

Military necessity, along with distinction, and proportionality, are three important principles of international humanitarian law governing the legal use of force in an armed conflict.

A belligerent is an individual, group, country, or other entity that acts in a hostile manner, such as engaging in combat. The term comes from the Latin bellum gerere (meaning "to wage war"). Unlike the use of belligerent as an adjective meaning "aggressive", its use as a noun does not necessarily imply that a belligerent country is an aggressor.

In times of war, belligerent countries can be contrasted with neutral countries and non-belligerents. However, the application of the laws of war to neutral countries and the responsibilities of belligerents are not affected by any distinction between neutral countries, neutral powers or non-belligerents.

In the context of war, perfidy is a form of deceptive tactic where one side pretends to act in good faith, such as signaling a truce (e.g., raising a white flag), but does so with the deliberate intention of breaking that promise. The goal is to trick the enemy into lowering its guard, such as stepping out of cover to accept a supposed surrender, only to exploit its vulnerability.

Perfidy constitutes a breach of the laws of war and so is a war crime, as it degrades the protections and mutual restraints developed in the interest of all parties, combatants and civilians.

Francis Lieber (born Franz Lieber; 18 March 1798 – 2 October 1872) was a German and American jurist and political philosopher. He is best known for the Lieber Code, the first modern codification of the customary law and the laws of war for battlefield conduct, which served as a basis for the Hague Conventions of 1899 and 1907 and for the later Geneva Conventions. He was also a pioneer in the fields of law, political science, and sociology in the United States.

Born in Berlin, Prussia, to a Jewish merchant family, Lieber served in the Prussian Army during the Wars of Liberation against Napoleon Bonaparte. He obtained a doctorate from the University of Jena in 1820. A republican, he volunteered to fight on the Greek side in the Greek War of Independence in 1821. After experiencing repression in Prussia for his political views, he emigrated to the United States in 1827. During his early years in America, he worked a number of jobs, including swimming and gymnastics instructor, editor of the first editions of the Encyclopaedia Americana, journalist, and translator.