Abstract
International Humanitarian Law (IHL) or the Law of Armed Conflict (LOAC), under the domain of public international law, consists of the rules and regulations of war/armed conflict applicable during an armed conflict, either of national or international character. IHL has played a great role to humanize warfare and regulate the conduct of parties to the war. This article seeks to explain how international humanitarian law can be understood and constructed from the two foundational principles, i.e., the principle of necessity and the principle of humanity. It is also to be noted that IHL is used when the emphasis is given more upon the humanitarian concerns, and LOAC is used when the emphasis is upon the military use of arms and weapons. 

Introduction
Public International Law has been seen as regulating three major domains: the Law of Peace, the Law of War, and the Law of Neutrality. International Humanitarian Law (IHL) or the jus in bello (law in war) is a body of international law that aims to regulate the conduct of States and individual participants in an armed conflict, regulating the means and methods of warfare. 
The law of armed conflict developed during a period when states could resort to force as a legitimate tool of state policy. ¹ However, in the present context, Article 2(4) of the UN Charter prohibits the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations.²  Nonetheless, it allows for the use of force for individual or collective self-defence if an armed attack occurs.³  The International Law simply cannot root out war or armed conflict, but it dictates that war must have limits and it must be humane. 
The LOAC applies to all parties to an armed conflict regardless of whether the party to the conflict violated the jus ad bellum to start the war in all circumstances without any adverse distinction based on the nature or origin of the armed conflict or on the causes accepted by or attributed to the Parties to the conflict.⁴  It must, however, be remembered that for IHL to come into effect, there must be an armed conflict either of International or non-international character. Riots, sporadic violence do not qualify for armed conflict, and IHL is not applicable in such situations. 
IHL seeks to strike a balance between the two main interdependent yet conflicting principles: (i) the principle of military necessity (ii) the principle of humanity. Other principles, such as distinction and proportionality, unnecessary suffering, are derivatives of humanity and necessity.⁵  In International law, there is no finality of what is a ‘core principle’ and what is not, and they are hardly agreed upon anonymously. For the purpose of this article, we will consider the principle of humanity and military necessity as foundational principles and construct the law of armed conflict as so.

Evolution of War:
‘Win the war with whatever it takes’ is a colloquial phrase used especially in times of war. In the World War I era, British Admiral John A. Jackie Fisher, referring to the Hague Convention of 1907, expressed that, ‘The essence of war is violence, and Moderation in war is imbecility’.⁶  Adolf Hitler secretly issued what is referred to as the Kommando Befehl, or Commando Order, which meant giving no quarter and summary execution,⁷  going all out in war to achieve his objectives. The essence lay in the maxim "Kriegsraison geht vor Kriegsmanier" which meant that the necessities of war take precedence over the rules of war.⁸  Whether the rules would be respected or ignored depended on the demands of the military situation at the time. The doctrine of "Kriegsraison" was still applied during the Second World War. Basically, under the classical notion, the war falls silent in times of war. 
These rules, however, are no longer in practice and have been superseded by the principle of military necessity and consideration for humanity, reaffirming the concept of modern ‘humane warfare’ under International Humanitarian Law.
(i)    The Principle of Military Necessity
The principle of Military necessity justifies fighting in the necessity of those measures which are indispensable for securing the ends of the war, and which are lawful according to the modern law and usages of war.⁹  In its broad sense, military necessity means ‘doing what is necessary to achieve a war aim’. It acknowledges the potential for unavoidable civilian death and injury ancillary to the conduct of legitimate military operations. 
A more exhaustive explanation of the concept of military necessity can be found in the Hostage Case from the post-Second World War:
“Military necessity permits a belligerent, subject to the laws of war, to apply any amount and kind of force to compel the complete submission of the enemy with the least possible expenditure of time, life and money. . . . It permits the destruction of life of armed enemies and other persons whose destruction is incidentally unavoidable by the armed conflicts of the war . . .  but it does not permit the killing of innocent inhabitants for revenge or the satisfaction of a lust to kill… There must be some reasonable connection between the destruction of property and the overcoming of the enemy forces.” ¹⁰
The essence of the Military necessity can be found in the 1907 Hague Regulations and the Rome Statute of the International Criminal Court.¹¹  Its status as customary law is indicated by the International Law Commission’s statement that it is one of the “obligations arising out of a peremptory norm of international law, i.e., a norm from which no derogation is permitted.” ¹²
However, the application of humanitarian principles does not override the needs of practical realism of war. Belief in humanitarian ideals does not result in an automatic rejection or dismissal of legitimate military needs.¹³  LOAC protects civilians, yet permits and justifies damages to civilians and civilian objects ancillary to military advantage if the advantage outweighs the damages to civilians. LOAC justifies such damages as collateral damage. But nonetheless, “Military convenience should not be mistaken for military necessity.” ¹⁴
(ii)    Principle of Humanity (The Martens clause and its legacy)
The principle of humanity imposes limits. The idea of the principle is understood as a limiting factor, the idea that there are, and should be, limits on war or the action of the conflicting parties. The idea central to this principle is the ‘Martens Clause’, which is the most famous acknowledgement of humanity in times of armed conflict. The Martens Clause, which is included in the preamble to both the 1899 and the 1907 Regulations, emerged from debate at the 1899 Conference over the status of resistance fighters who take up arms against an occupying authority (levee en masse). 
As affirmed in the S.S. Lotus case (1927), in international law, States are free to act unless there is a specific rule prohibiting their actions.¹⁵  If something is not expressly prohibited by international law, it is permitted. However, that would not be the case for IHL. The Martens clause requires that even in the absence of such prohibitions under IHL, the conduct of parties to the conflict must be guided by principles of humanity and the dictates of public conscience.
In absence or lack of clear provision on regulations relating to war, populations and belligerents remain under the protection and empire of the principles of international law, as they result from the usages established between civilized nations, from the laws of humanity, and the requirements of the public conscience which is known as the Martens Clause.¹⁶  The principle of humanity is an explicit rejection of the nineteenth-century doctrine of Kriegsraison¹⁷,  and that ‘belligerents, even individual combatants, have the right to do whatever is required to prevail in armed conflict; to do whatever they believe is required to win.¹⁸
Article 1, paragraph 2, of Additional Protocol 1 of 1977, which reads as follows: "In cases not covered by this Protocol or by other international agreements, civilians and combatants remain under the protection and authority of the principles of international law derived from established custom, from the principles of humanity and from the dictates of public conscience." 
The Martens clause as affirmed by the ICJ, has elevated to the status of customary international law.¹⁹  The ICTY further highlighted the role of the principle of humanity “As a minimum, reference to those principles and dictates any time a rule of international humanitarian law is ‘not sufficiently rigorous or precise’: in those instances, the scope and purport of the rule must be defined with reference to those principles and dictates.” ²⁰  Further the principles of international humanitarian law may emerge through a customary process under the pressure of the demands of humanity or the dictates of public conscience, even where State practice is scant or inconsistent. ²¹
In the Kupreskic case, the court used the Martens clause to entail that the prescriptions of customary rules must be interpreted to construe as narrowly as possible the discretionary power to attack belligerents, and by the same token, to expand the protection given to civilians. ²²

Balancing the Principle of military necessity and Humanity
The two fundamental principles — military necessity and humanity — form the core tension and balance of IHL. As Professor Sassòli notes, “IHL is a compromise between humanity and military necessity, a compromise which cannot always satisfy humanitarian agendas, but which has the immense advantage that it has been accepted by states as law that can be respected, even in war.”²³  And as the ICJ put it, that it is undoubtedly a great many rules of humanitarian law applicable in armed conflict are so fundamental to the respect of the human person and elementary considerations of humanity.’ ²⁴
The principle of military necessity and humanity creates tension, as you can fight but within limits. All other principles, like the principle of distinction, proportionality, and unnecessary suffering, flow from trying to balance these two. As in the principle of distinction, the parties to the conflict must distinguish between military targets and civilians (a humanity protection) and only target combatants or military objects (a military necessity principle). Similarly, in the principle of proportionality, combatants can attack legitimate targets (necessity), but must not cause excessive harm to civilians compared to the expected military advantage. (Humanity constraint). Again, it is prohibited to cause unnecessary suffering in war, necessity allows parties to weaken the enemy, but not in a cruel and pointless manner. (Humanity constraint). 
Even though these principles conceptually express the balance between necessity and humanity, in modern treaties and customary law, they exist as independent principles with their own binding force in law.
The entire structure of IHL is the balancing of the two imperative principles. Even all IHL treaties regulating warfare can be seen as an attempt to regulate military necessity through the lens of humanity or vice versa. For example, the Geneva Conventions of 1949 and their Additional Protocols can be seen as the balance of the imperatives as they require humane and regulated treatment of wounded soldiers, prisoners of war, and civilians. The Geneva Convention reflects the principle of humanity: protecting the lives of people who are not taking part in hostilities, dignity, and basic rights. Similarly, under the strike of necessity, the adverse party can be captured or attacked, and some even lose protected status when they resume hostile activities (like a civilian who takes direct part in hostility). Similarly, the Hague law regulating the conduct of hostility, including the means and methods of warfare, can also be seen to operationalize the principle of military necessity and humanity. The greatest strength of IHL, as pointed out by the ICJ, is that it is designed in such a way that it applies to all forms of warfare and to all kinds of weapons, including those of the future.²⁵

Conclusion
The principle of military necessity and the principle of humanity form the core tension and balance of the International Humanitarian Law. Most treaty provisions under IHL and principles can be seen as either permitting military actions necessary or constraining actions to prevent unnecessary human suffering. In conformity with the aforementioned principles, humanitarian law, at a very early stage, prohibited certain types of weapons either because of their indiscriminate effect on combatants and civilians or because of the unnecessary suffering caused to combatants, that is to say, a harm greater than that unavoidable to achieve legitimate military objectives. IHL applies to all forms of warfare and to all kinds of weapons, including those of the future. Critically, IHL does not merely regulate the weapons and tactics of today; it is a living framework. Thus, these principles govern all forms of warfare, present and future. It is through the uncompromising application of these principles that the LOAC demands that even at war, humanity must never be forsaken.