The fundamental rule establishing the scope of application of international humanitarian law states that it is applicable in international armed conflicts. When there is an armed conflict, the international law of peace existing between the states concerned will largely be superseded by the rules of international humanitarian law. The international law of peace, however, will continue to be of great importance, particularly for the relationship between the parties to a conflict and neutral states.

If the application of international humanitarian law is dependent up on the existence of armed conflict, it becomes, therefore, essential to see what this phrase actually refers to. Traditional international law was based upon a rigid distinction between the state of peace and the state of war. Countries were judged as either in a state of peace or a state of war and there were no intermediate states, although there were cases in which it was difficult to tell whether the transition to a state of war has been made. So long as two countries were at peace, the law of peace – the normal rules of international law ---govern relations between them and if once they enter the state of war, the law of peace ceases to apply and their relations with one another become subject to the law of war, while their relations with other states not party to the dispute will be governed by the law of neutrality.

No such clear picture can be discovered today as since 1945, countries have rarely regarded themselves as being in a formal state of war. In response to this changing scenario, international humanitarian law now becomes applicable as soon as there is an international armed conflict without being subject to how the states party to the conflict define their status. There is also no sharp dichotomy between peace and armed conflict in international law such as used to exist between peace and war. A state of war usually presumed a complete a rupture of normal relation between the parties though today armed conflict between two countries does not necessarily mean that all non- hostile relations between them cease unlike what had been assumed widely in the past.  Today neither an armed conflict nor a formal state of war has such an effect. Thus, diplomatic relations between the parties will not necessarily be terminated or suspended because there is armed conflict between them.

Coming back to our main concern, it is now well established that the application of international humanitarian law is not dependent upon the existence of a formal state of war, or indeed upon the existence of what has sometimes been called ‘war in the factual sense’. The Geneva Conventions that provide the applicability of the rules of international humanitarian law as governed by Common Art. 2 Para. I, provide that the conventions apply to all cases of declared war or another armed conflict which may arise between two or more of High Contacting parties even if the state of war is not recognized by one of them. Although the final phrase does not deal expressly with the situation in which neither party to an armed conflict admits that it is in a state of war, it is generally believed that the Conventions were intended to apply in such a case, so that the last phrase should be read as if it said even if the state of war is not recognized by one or both of them. That is certainly the way in which it was interpreted in practice in most conflicts since 1949 as neither side has admitted that it was in a state of war, yet they have treated the Geneva Conventions as applicable. The Conventions are also applicable in a case where a sate declares war but does not engage in actual hostilities as was the case with some Latin American states during World War II.

The Hague Conventions of 1907 and a number of other earlier treaties on humanitarian law are stated to apply only in time of war. In practice, however, the rules which they contain are treated as applicable in an international armed conflict, whether or not that conflict is regarded by the parties as a war or not.

The Geneva Conventions do not define armed conflict and this omission was said to be apparently deliberate, since it was hoped that this term would continue to be purely factual and not become laden with legal technicalities. The ICRC Commentary on the Geneva Conventions takes a very broad view of what constitutes an armed conflict. It provides that any difference arising between two states and leading to the intervention of the members of the armed forces is an armed conflict even if one of the parties denies the existence of a state of war. It makes no difference how long the conflict lasts, or how much slaughter takes place. It will generally be stated therefore that when fighting reaches a level of intensity which exceeds that of isolated clashes it will be treated as an armed conflict to which the rules of international humanitarian law apply. And that in any event, only the use of force by the organs of a state, rather than by private persons, will constitute an armed conflict.

Generally speaking, the application of international humanitarian law is not dependent on a formal declaration of war that nowadays occur only occasionally. It has already been noted that international humanitarian law now becomes applicable in any international armed conflict, whether or not a state of war exists between the parties. It follows that a declaration of war is not necessary for the application of humanitarian law. In fact, there are cases in which declaration of war have been delivered by one state to another through diplomatic channels as was done in World War I and II. But in most cases the parties to a conflict had denied that they were in a state of war. There have, however, been cases in which states have expressed the view, by means other than a formal declaration, that they regarded themselves as being at war. Thus, in both 1948 and 1967 a number of Arab states made explicit stamens to the effect that they were at war with Israel, and similar statements were made by Iran and Iraq during the 1980-88 Iran-Iraq War, as well as by Pakistan during its 1965 conflict with India.

It has also been established that it is irrelevant to the validity of international humanitarianly law whether the States and Governments involved in the conflict recognize each other as States. Because the applicability of the rules of international humanitarian law is not dependent upon whether the parties to a conflict recognize one another as states or not. Throughout the Arab-Israel conflict, for example, the Arab sates have not recognized Israel as a state; yet, both sides in that conflict have accepted the application of international humanitarian law. The question of whether the parties to an armed conflict are sates is said to be objective and not a matter to be determined by the subjective recognition policies of each party hence it is not important to determine the parties as states for the rules of international humanitarian law to apply

In addition, the application of humanitarian law in international armed conflicts does not depend on whether an armed conflict has been started in violation of a provision of international law, e.g. the prohibition against aggressive war. The victims of military aggression contrary to international law are also bound by the rules of international humanitarian law. Hence, the governing rule of international humanitarian law in this respect provides that it shall apply equally to all the parties to an armed conflict, irrespective of which state was responsible for starting the conflict and of whether that State was guilty of an act of aggression based on the rules of public international law.

Looking at the issue from a different perspective, there are cases in which the UN may resort to use force in its peace-keeping operations and other military operations. The issue that comes into picture in this case is whether this international humanitarian law shall be observed in peace keeping operations and other military operations of the United Nations or whether it is an exception. Although there was originally some doubt about the applicability of international humanitarian law to UN forces, it is now generally accepted that such  forces are subject to humanitarian law, whether they were established as peace-keeping forces or for the purpose of engaging in enforcement action. Thus, the Institute de droit international has confirmed that the humanitarian rules of the law of armed conflict apply to the United Nations as of rights and they must be complied with in every circumstance by United Nations forces which are engaged in hostilities. A second Institute resolution maintains that this obligation also extends to those rules of the law of armed conflict which are not of a specifically humanitarian character. Given that this is the case when the UN establishes a force of its own, it is clear that the rules of humanitarian law are applicable to a force under national control which operates with the authority of the Security Council.

There are cases in which the armed conflict remains non-international when there is no other state involved in the conflict. An armed conflict is said to be non-international if it is a confrontation between the existing governmental authority and groups of persons subordinate to this authority and is carried out by force of arms within national territory and reaches the magnitude of an armed riot or a civil war. Now, the question is whether the scope of application of international humanitarian law also encompasses this kind of conflict.

In non-international armed conflict, each party shall be bound to apply, as a minimum, the fundamental humanitarian provisions of international law embodied in the four 1949 Geneva Conventions, the 1954 Cultural Property Convention, and the 1977 Additional Protocol II. German soldiers, for example, like their Allies, are required to comply with the rules of international humanitarian law in the conduct of military operations in all armed conflicts. However, such conflicts are characterized, i.e. irrespective of whether that conflict is characterized as internal or international.

This rule setting for the application of international humanitarian law to non-international armed conflicts was only embodied in treaty form for the first time in the 1949 Geneva Conventions. Today, there are two instruments which expressly apply to non-international armed conflicts. Common Art. 3 of the Geneva Conventions contains a series of rudimentary provisions dealing with minimum rights and duties, such as the requirements that those hors de combat be treated humanely and that the wounded and sick be collected and cared for, and the prohibition against murder, torture, hostage taking, humiliating and degrading treatment, and the passing of sentences and carrying out of executions without a fair trial. AP II is a far more detailed code for application in internal armed conflicts.

 ICRC has provided a definition of humanitarian law in a more comprehensive manner enabling the reader to understand the scope of application of the law. It defines it as those international rules established by treaty of custom which are specifically intended to solve humanitarian problems directly arising from international or non-international armed conflicts and which, for humanitarian reasons, limit the right of the parties to a conflict to use methods and means of warfare of their choice or protect persons and property that are, or may be, affected by the conflict.

This definition, no doubt, requires some explanation. Therefore, we have to  discuss it in brief. The aim of international humanitarian law is to protect the human being and to safeguard the dignity of man in the extreme situation of war. The provisions of international humanitarian law have always been tailored to fit human requirements. They are bound to the aspiration of the protection of man from the consequences of brute force. The duty to respect the individual takes on special significance when the perpetrator of the violence is the State. Clearly, therefore, international humanitarian law is a part of that branch of international law safeguarding human rights from abuse by State power.

As is the case with every rule of law, the provisions of international humanitarian law are the result of a compromise, i.e. the weighing of conflicting interests. International humanitarian law must make allowance for the phenomenon of war and legitimate military goals. We call this the criterion of military necessity. On the other hand, the individual who does not or no longer participate in the hostilities must be protected as best as possible. The conflicting interests of military necessity and humanitarian considerations can be death within rules which limit the use of force in war but do not prohibit it when such use is legitimate. In this case, only international humanitarian law can do the best possible and can even set forth absolute prohibitions in the cases of, for example, torture  which is forbidden in all circumstances, without exception.

We can, therefore, infer that humanitarian law will only be endorsed by those responsible for using military force if it takes into account military considerations. In the real world, therefore, humanity must always take into consideration requirements of military necessity. In this, the law does not sanction the use of brute force; it reflects a desire to set realistic limits to the use of force which can be successfully applied. It is not the purpose of international humanitarian law to prohibit war or to adopt rules rendering war impossible. Rather, international humanitarian law must reckon with war, the better to keep the effects thereof within the boundaries of absolute military necessity.