Learn more about Religious war
A religious war is a war justified by religious differences. It can be the legitimate forces of one state that has an established religion against those of another state with either a quite different religion or a different sect within the same religion, or, at the level below a state, it can be a faction motivated by religion attempting to spread its faith by violence either within the state or elsewhere. The European Wars of Religion, the Crusades, and the Reconquista are frequently cited historical examples.
While there are undoubtedly wars fought primarily on religious grounds, wars frequently have multiple and complex causes. Saint Augustine is credited as being the first to detail a "Just War" theory within Christianity, whereby war is justifiable on religious grounds. Saint Thomas Aquinas elaborated on these criteria and his writings were used by the Roman Catholic Church to regulate the actions of European countries. In modern times religious designations are frequently used as shorthand for cultural and historical differences between combatants, giving the impression that the conflict is primarily about religious differences. For example, The Troubles in Northern Ireland are frequently seen as a conflict between Catholic and Protestant. However, the more fundamental cause is the attachment of Northern Ireland to either the Republic of Ireland or the United Kingdom. As the native Irish were mostly Catholic, and the later English-sponsored immigrants mainly Protestant, the terms become shorthand for the two cultures. It cannot be denied, however, that religion does play a part in the conflict, since churches are used as organizing points for demonstrations, and Protestants are far more likely to oppose union with the Catholic-dominated Republic.
 Religion and War
Many wars that are not Religious wars, often still include elements of religion such as priests blessing battleships. Also differences in religion can further inflame a war being fought for other reasons. Historically temples have been military targets that are destroyed to weaken the morale of the opponent, even when the war itself is not being waged over religious ideals.
The view upon religions versus another is very debatable. For example, in the USA, and in other places around Europe, many people would agree that terrorism is part of an ongoing war of religion. However, who is fighting who is the main topic that is so hard to define. Is it Muslims vs. Christianity? Or is it the Middle East vs. The West? Many people have different views, definitions and opinions upon this subject.
Jihad is to strive or struggle in the way of God, and is sometimes referred to as the sixth pillar of Islam, although it has no official status.<ref name="jih">John Esposito(2005), Islam: The Straight Path, pp.93</ref> Jihad has a wider meaning in Islamic literature. It can be striving to lead a good Muslim life, praying and fasting regularly, being an attentive spouse and parent or working hard to spread the message of Islam.<ref>John Esposito(2002). Unholy war: terror in the name of Islam, Oxford University Press, US. ISBN 0195154355. pp.26</ref> Jihad is also used in the meaning of struggle for or defence of Islam, the holy war. Despite the fact that Jihad is not supposed to include aggressive warfare, this has occured, as exemplified by early extremists like Kharijites and contemporary groups like Egypt's Jihad Organization (which assasinated Anwar Al Sadat) as well as Jihad organizations in Lebanon, the Gulf states, and Indonesia.<ref name="jih"/>
In Muhammad's time, after Itmam al-hujjah (completion of the proof, a doctrine in Islam related to prophets), polytheists of Arabia were asked for submission to Islam as a condition for exoneration and the others for jizya and submission to the political authority of the Muslims for exemption from death punishment and for military protection as the dhimmis of the Muslims.<ref name="jjihad">Ghamidi, Javed (2001). “The Islamic Law of Jihad”, Mizan. Dar ul-Ishraq. OCLC 52901690.</ref> Islamic scholars have different opinions on Jihad, however, there is a consensus that armed struggle against persecution and oppression will always continue.<ref name="jjihad"/>
The Crusades were a series of military campaigns—usually sanctioned by the Papacy—that took place during the 11th through 13th centuries. Originally, the aim was to recapture Jerusalem and the Holy Land from the Muslims and at supporting the Byzantine Empire against the Muslim Seljuq expansion into Asia Minor. The fourth crusade however was diverted and resulted in the conquest of Constantinople. Later on, Crusades were launched against other targets, either for religious reasons, such as the Albigensian Crusade, the Northern Crusades, or because of political conflict, such as the Aragonese Crusade. In 1095, at the Council of Clermont, Pope Urban II raised the level of war from Bellum iustum ("just war"), to bellum sacrum.<ref>Christian Jihad: The Crusades and Killing in the Name of Christ</ref>
 Milhemet Mitzvah
The Judaic term for a holy war. The way of declaring one is outlined in the Hebrew Bible.