Up to this day, the conduct of hostilities has brought terrible suffering to mankind. Thousands of combatants and fighters have been traumatized, injured, or killed. Civilians have lost their belongings, their loved ones, and their lives. For more than 100 years, IHL has therefore had the primary objective to regulate the conduct of hostilities and to minimize the suffering caused by war. As a result, IHL has developed an extensive body of rules on the means and methods of warfare. The means of warfare refer to the types of weapons that are developed, possessed and used during armed conflict. The methods of warfare, on the other hand, concerns specific ways in which such weapons are used or in which hostilities can be conducted. IHL either restricts or prohibits certain means and methods of warfare on the basis of the long standing rule of limited warfare which rejects total war by providing the following and I quote, the right of the Parties to the conflict to choose methods or means of warfare is not unlimited. This rule reflects the basic idea underlying IHL that any act of war must balance the concerns of humanity on the one hand, and military necessity on the other hand. The rule of limited warfare was initially qualified in Article 22 of the 1907 Hague regulations. And later, restated in Article 35, paragraph 1 of the 1977 Additional Protocol I (API). API applies to international conflicts and is to date ratified by 174 states. The rule undisputedly forms part of customery international law. There are a few important principles which follow from this rejection of total war, namely, those of distinction, proportionality, and precautions, and the prohibition of unnecessary suffering. Many other rules are built upon these fundamental principles. In this lecture, we will examine the principle of distinction in greater detail. According to the principle of distinction, the parties to the conflicts must at all times distinguish between civilians and combatants, and between civilian objects and military objectives. Attacks may only be directed against combatants and military objectives. Thus, in general, it is prohibited to carry out attacks against civilians and civilian objects. The aim of this principle is to protect the civilian population from the dangers arising from military operations. The principle is codified in Article 48, and Article 51, paragraph 2, as well as Article 52, paragraph 2 of API. This rule is also considered to form part of customary international law. Thus, now that we have established that the parties to a conflict must distinguish at all time between civilians and combatants and between civilian objects and military objectives, it is important to explore what these terms actually mean. So how do we define combatants? Combatants are described by Additional Protocol I as the members of the armed forces of a party to an international armed conflict with the exception of medical and religious personnel. Equally, Article 4A, paragraph 1 of the third Geneva Convention defines Prisoners of War as members of the armed forces of a party to the conflict as well as members of militias and volunteer corps forming part of such armed forces who have fallen into the hands of the enemy. However, IHL recognizes that the rights and duties of war do not only apply to the regular armed forces, but can extend to other organized armed groups in an international armed conflict, such as militias or volunteer corps. Members of these other organized armed groups also receive combatant status provided that they fulfill the following four conditions, assimilating them to the regular armed forces. First, they need to be commanded by a person responsible for his subordinates. Second, they need to have a fixed distinctive sign recognizable at a distance. Third, they need to carry arms openly and fourth, they must conduct their operations in accordance with words of IHL. There are three legal consequences for combatants that result from their combatant status. First, as follows from the principles of distinction, combatants are legitimate military objectives or targets, meaning that they may be lawfully attacked at any time during armed conflict. Second, combatants enjoy combatant privilege, which means that they have the right to use lawful means and methods of warfare. They can thus directly participate in hostilities without facing criminal prosecution. Finally, and thirdly, combatants who fall into the hands of the enemy are entitled to Prisoner of War status. We have now looked at what it means to be a combatant, but how do we define the term civilians? API provides a negative definition of civilians. In other words, it states that civilians are persons who are not combatants. In case of doubt about the person's status, that person must be considered a civilian. Civilians are protected by the principal of distinction. And as a result, they may not be attacked by the parties to a conflict. However, exceptionally, they may be attack for such time as they take a direct part in hostilities. We will discuss this exception in greater detail in our lecture on non-international armed conflicts. Now that we have discussed the meaning of the terms combatant and civilian, we will consider the concept of civilian objects and military objectives. What are military objectives? An object must meet two cumulative criteria to qualify as a military objective pursuant to Article 52, paragraph 2 of Additional Protocol I, which reflects customary IHL. First, an item must contribute effectively to the enemy's military action. It has to do so by its nature, location, purpose, or current use. Second, the destruction, capture, or neutralization of such an object must offer the attacker a definite military advantage in the sense that the military advantage must be concrete and perceptible. Examples of military objectives are buildings and positions where enemy combatants and their material and weapons are located, such as Military barracks. Other examples include military means of transportation, like tanks or fighter jets, and means of communication such as broadcasting stations, although the latter depends on contextual factors. But which objects are civilian in nature? Like civilians, civilian objects are also negatively defined and encompass all objects which are not military. This straightforward definition has the advantage that it eliminates the possibility of a further category of objects thereby leaving no room for doubt as to whether an object can be attacked or not. Generally, cities, residential areas, buildings, houses, schools, hospitals, and historic monuments are among others considered as civilian objects. So why again is the distinction between civilians and combatants as well as between civilian objects and military objectives important to us? As we already noted in API, the principle of distinction prohibits, first and foremost, direct attacks against civilians and civilian objects. But another prohibition derived from the principle of distinction is the prohibition of indiscriminate attacks as found in Article 51, Paragraph 4 of API. And this includes attacks which cannot be directed at specific military objectives. Consequently, they strike military objectives and civilians and civilian objects without distinction. Examples of indiscriminate attacks are listed in Article 51, paragraph 5 of API, and include for instance, an attack by bombardment, which treats as a single military objective, a number of clearly separated and distinct military objectives located in the city, town, village, or other area containing a similar concentration of civilians, or civilian objects. To conclude this lecture, in order to protect victims of war as much as possible, there are restrictions placed upon the weapons that are used in armed conflict, the ways in which these weapons are used and the manner in which hostilities can be conducted. Regarding the letter, it is crucial to always distinguish between combatants and civilians, and between civilian objects and military objectives.