The conduct of war is regulated by certain well-established and recognised rules that are usually designated as “the laws of war,” which comprise the rules, both written and unwritten, for the carrying on of war, both on land and at sea.

During the past 50 years many of these rules have been reduced to writing by means of conventions or treaties entered into by the principal civilised nations of the world after full discussion at The Hague, Geneva, Brussels, and St. Petersburg.

These rules relate to war on land, and the principal written agreements relating to the conduct of war on land are:

1. The declaration of St. Petersburg of the 11 December 1868 forbidding in time of war the use of explosive projectiles under 400 grams weight.
2. The Declaration of The Hague of 29 July 1899 preventing the employment of projectiles which have for their only object the diffusion of asphyxiating or deleterious gases (This was never ratified by the US).
3. The Declaration of The Hague of 29 July 1899 preventing the employment of bullets which expand or flatten in the human body.
4. The Geneva Convention of 06 July 1906 for the amelioration of the condition of the sick and wounded of armies in the field.
5. Convention No. III of The Hague of 18 October 1907 with regard to the opening of hostilities.
6. Convention N. IV of The Hague of 18 October 1907 concerning the laws and customs of war on land.
7. Convention No. V of The Hague of 18 October 1907 concerning the rights and duties of neutral powers and person in war on land.
8. A portion of the Convention No. IX of The Hague of 18 October 1907 concerning the bombardment by naval forces in time of war.
9. Convention No. VIII of The Hague of 18 October 1907 relative to the laying of submarine mines.
10. A portion of Convention No. XI of The Hague of 18 October 1907 relative to the right of capture in naval warfare.
11. The declaration of The Hague of 18 October 1907 prohibiting the discharge of projectiles and explosives from balloons.

The foregoing do not constitute a complete code as appears from the preamble of Convention IV of October 18, 1907:

According to the views of the high contracting parties, these provisions, the preparation of which has been inspired by the desire to diminish the evils of war, as far as military requirements permit, are intended to serve as a general rule of conduct for the belligerents in their mutual relations and in their relations with the inhabitants.

It has not, however, been found, possible at present to prepare regulations covering all the circumstances which may arise in practice.

On the other hand, the high contracting parties clearly do not intend that unforeseen cases should, in the absence of written undertaking, be left to the arbitrary judgement of military commanders.

Until a more complete code of the laws of war has been formulated, the high contracting parties deem it expedient to declare that, in cases not covered by the regulations’adopted by them, the inhabitants and belligerents remain under the protection and the rule of the principles of the law of nations, as they result from the usages established among civilised peoples, from the laws of humanity, and the dictates of public conscience.

The contracting powers of rules shall issue instructions to their armed land forces which shall be in conformity with the regulations respecting the laws and customs of war on land, annexed to the present convention. (US Army, 1914, p.11-13).

Reference

US Army. (1914) Rules of Land Warfare. Available from World Wide Web: http://www.loc.gov/rr/frd/Military_Law/pdf/rules_warfare-1914.pdf. [Accessed: 28 September, 2015].