Introduction War has been defined as a clash between two groups which involves intentional use of arms in fighting each other, mostly for political gains. War is a brutal and cruel way to solve some state problems. For example, people have used war to determine who benefits from which resources in the country or who controls certain parts of or the entire the country. For any place to be termed as war zone, there has to be people who have willfully and consciously decided that they are going to engage in warfare, and this has to take place in reality and not just remain as an intention that is yet to be executed. Certain questions have been raised by different scholars concerning the concept of war. For instance, can there be a time when war is necessary and the right thing to do? Is it possible for war to be completely eradicated? In case of war in a state, what are the necessary measures to be taken by the state to ensure that its citizens enjoy normal privileges in life? In this paper, the concept of war, with specific reference to the crusades is discussed. Just war The just war theory is one of the renown theories about war. This theory has been supported by a number of people for example, Saint Augustine, Aquinas and many other influential historical figures. It is believed that Augustine was the pioneer of this theory, although it is not very clear whether there were others involved in the formulation of the theory. This theory has raised many arguments both about its morality and legality. The just war theory has three major sections. They are jus ad bellum which deals with reasons as to why going to war against another state may be justified, jus in bello which stipulates how those involved in wars should conduct themselves and jus post bellum which deals with the post war requirements. Jus ad bellum mostly deals with the head of state. This is considered as the most important among the three sections of the just war theory. Under this principle, several things are needful before there is declaration of war by the head of state. For instance, there must be a just cause as to why the state has opted to use war as a toll for finding solution. A just cause would be for example, defending the country against enemies who may have already struck them, defending the citizens against violation of their human rights through brutal attacks. Some proponents of the just war theory suggest that the only just cause for any state to engage in war is because of something terribly immoral and incorrect done to them. Other proponents of the theory suggest that the only reason a state would be justified to engage in war against another is in self defense from an attack which leads to abuse of the rights of people. These rights could be the rights of every citizen or the rights of a state. The rights of a state are stipulated in the international law which gives every state a right to political independence. The states also enjoy the right of being in charge of its territory and any outside attempt to rob it of this right might lead to war if there is no any other peaceful means of resolving the conflict. The invaders of another state’s territory hence may not enjoy any rights as the invaded territory is forced to resist their attack violently. According to Brad (2001,10), It is important for the state to have these righ