Hague Convention of 1907 in the context of "No quarter"

Military occupation, also called belligerent occupation or simply occupation, is temporary hostile control exerted by a ruling power's military apparatus over a sovereign territory that is outside of the legal boundaries of that ruling power's own sovereign territory. The controlled territory is called occupied territory, and the ruling power is called the occupant. Occupation's intended temporary nature distinguishes it from annexation and colonialism. The occupant often establishes military rule to facilitate administration of the occupied territory, though this is not a necessary characteristic of occupation.

The rules of occupation are delineated in various international agreements—primarily the Hague Convention of 1907, the Geneva Conventions, and also by long-established state practice. The relevant international conventions, the International Committee of the Red Cross, and various treaties by military scholars provide guidelines on topics concerning the rights and duties of the occupying power, the protection of civilians, the treatment of prisoners of war, the coordination of relief efforts, the issuance of travel documents, the property rights of the populace, the handling of cultural and art objects, the management of refugees, and other concerns that are highest in importance both before and after the cessation of hostilities during an armed conflict. A country that engages in a military occupation and violates internationally agreed-upon norms runs the risk of censure, criticism, or condemnation. In the contemporary era, the laws of occupation have largely become a part of customary international law, and form a part of the law of war.

War reparations are compensation payments made after a war by one side to the other. They are intended to cover damage or injury inflicted during a war. War reparations can take the form of hard currency, precious metals, natural resources, industrial assets, or intellectual properties. Loss of territory in a peace settlement is usually considered to be distinct from war reparations.

War reparations are often governed by treaties which belligerent parties negotiate as part of a peace settlement. Payment of reparations often occur as part of a condition to remove occupying troops or under the threat of re-occupation. The legal basis for war reparations in modern international law is Article 3 of the Hague Convention of 1907.

The use of toxic chemicals as weapons dates back thousands of years, but the first large-scale use of chemical weapons was during World War I. They were primarily used to demoralize, injure, and kill entrenched defenders, against whom the indiscriminate and generally very slow-moving or static nature of gas clouds would be most effective. The types of weapons employed ranged from disabling chemicals, such as tear gas, to lethal agents like phosgene, chlorine, and mustard gas. These chemical weapons caused medical problems. This chemical warfare was a major component of the first global war and first total war of the 20th century. Gas attack left a strong psychological impact, and estimates go up to about 90,000 fatalities and a total of about 1.3 million casualties. However, this would amount to only 3–3.5% of overall casualties, and gas was unlike most other weapons of the period because it was possible to develop countermeasures, such as gas masks. In the later stages of the war, as the use of gas increased, its overall effectiveness diminished. The widespread use of these agents of chemical warfare, and wartime advances in the composition of high explosives, gave rise to an occasionally expressed view of World War I as "the chemist's war" and also the era where weapons of mass destruction were created.

The use of poison gas by all major belligerents throughout World War I constituted war crimes as its use violated the 1899 Hague Declaration Concerning Asphyxiating Gases and the 1907 Hague Convention on Land Warfare, which prohibited the use of "poison or poisoned weapons" in warfare. Chemical weapons in World War II saw widespread use by Germany during the Holocaust and by Japan against China. Battlefield use against Western Allies was prevented by deterrence.

The French ruse de guerre, sometimes literally translated as ruse of war, is a non-uniform term; generally what is understood by "ruse of war" can be separated into two groups. The first classifies the phrase purely as an act of military deception against one's opponent; the second emphasizes acts against one's opponent by creative, clever, unorthodox means, sometimes involving force multipliers or superior knowledge. The term stratagem, from Ancient Greek strategema (στρατήγημα, 'act of generalship'), is also used in this sense.

Ruses de guerre are described from ancient to modern times, both in semi-mythical accounts and in well-documented events; they also feature in fiction. The term ruse de guerre is given legal meaning within the rules of war. Good faith is required, but at least 17 different types of ruse, including ambushes, false radio messages, the use of spies and the use of dummy guns, are considered legitimate as long as they do not involve treachery or perfidy. Landmines and similar traps can be considered perfidious under the rules in certain circumstances. Explicitly prohibited ruses under article 23 of the Hague Convention of 1907 include improper use of a flag of truce or the military insignia of the enemy.