"The sacred warrior conquers the world not through violence or aggression, but through gentleness, courage, and self-knowledge. The warrior discovers the basic goodness of human life and radiates that goodness out into the world for the peace and sanity of others.......There is a basic human wisdom that can help solve the world’s problems. It doesn’t belong to any one culture or region or religious tradition—though it can be found in many of them throughout history. It’s what Chögyam Trungpa called the sacred path of the warrior."
"A religious war or holy war (Latin: bellum sacrum) is a war primarily caused or justified by differences in religion. The account of the conquest of Canaan by the Israelites in the Book of Joshua, the Muslim conquests of the 7th and 8th centuries, and the Christian Crusades (11th to 13th centuries) and Wars of Religion (16th and 17th centuries) are sometimes classified as examples. A religious aspect has been part of warfare in some cultures as early as the battles of the Mesopotamian city-states."
"The European war against Muslim expansion was recognized as a "religious war" or bellum sacrum from the beginning. The early modern wars against the Ottoman Empire were seen as a seamless continuation of this conflict by contemporaries.....The term "religious war" was used to describe, controversially at the time, what are now known as the European wars of religion, and especially the then-ongoing Seven Years' War, from at least the mid 18th century."
"Religious wars account for less than 2% of all people killed in warfare. This includes 3 million during the Crusades and 3,000 during the Inquisition.".... Lurie, Alan. "Is Religion the Cause of Most Wars?". Huffington Post.
In early Christianity, St. Augustine's concept of just war (bellum iustum) was widely accepted, but warfare was not regarded as a virtuous activity and expressions of concern for the salvation of those who killed enemies in battle, regardless of the cause for which they fought, was common. According to historian Edward Peters, before the 11th century Christians had not developed a concept of "Holy War" (bellum sacrum), whereby fighting itself might be considered a penitential and spiritually meritorious act. During the 9th and 10th centuries, multiple invasions occurred which lead some regions to make their own armies to defend themselves and this slowly lead to the emergence of the Crusades, the concept of "holy war", and terminology such as "enemies of God" in the 11th century.
During the time of the Crusades, some of those who fought in the name of God were recognized as the Milites Christi, soldiers or knights of Christ. The Crusades were a series of military campaigns that took place during the 11th through 13th centuries against the Muslim Conquests. Originally, the goal was to recapture Jerusalem and the Holy Land from the Muslims, and support the besieged Christian Byzantine Empire against the Muslim Seljuq expansion into Asia Minor and Europe proper. Later, 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 ("holy war"). In 16th Century France there was a succession of wars between Roman Catholics and Protestants (Hugenots primarily), known as the French Wars of Religion. In the first half of the 17th century, the German states, Scandinavia (Sweden, primarily) and Poland were beset by religious warfare in the Thirty Years War. Roman Catholicism and Protestantism figured in the opposing sides of this conflict, though Catholic France did take the side of the Protestants but purely for political reasons.
The Battle of Las Navas de Tolosa, known in Arab history as the Battle of Al-Uqab (معركة العقاب), took place on 16 July 1212 and was an important turning point in the Reconquista and in the medieval history of Spain.The forces of King Alfonso VIII of Castile were joined by the armies of his Christian rivals, Sancho VII of Navarre, Pedro II of Aragon and Afonso II of Portugal in battle against the Berber Muslim Almohad conquerors of the southern half of the Iberian Peninsula.
The Muslim conquests were a military expansion on an unprecedented scale, beginning in the lifetime of Muhammad and spanning the centuries, down to the Ottoman wars in Europe. Until the 13th century, the Muslim conquests were those of a more or less coherent empire, the Caliphate, but after the Mongol invasions, expansion continued on all fronts (other than Iberia which was lost in the Reconquista) for another half millennium until the final collapse of the Mughal Empire in the east and the Ottoman Empire in the west with the onset of the modern period.
There were also a number of periods of infighting among Muslims; these are known by the term Fitna and mostly concern the early period of Islam, from the 7th to 11th centuries, i.e. before the collapse of the Caliphate and the emergence of the various later Islamic empires.
While technically, the millennium of Muslim conquests could be classified as "religious war", the applicability of the term has been questioned. The reason is that the very notion of a "religious war" as opposed to a "secular war" is the result of the Western concept of the separation of Church and State. No such division has ever existed in the Islamic world, and consequently there cannot be a real division between wars that are "religious" from such that are "non-religious". Islam does not have any normative tradition of pacifism, and warfare has been integral part of Islamic history both for the defense and the spread of the faith since the time of Muhammad. This was formalised in the juristic definition of war in Islam, which continues to hold normative power in contemporary Islam, inextricably linking political and religious justification of war. This normative concept is known as Jihad, an Arabic word with the meaning "to strive; to struggle" (viz. "in the way of God"), which includes the aspect of struggle "by the sword",
The first forms of military Jihad occurred after the migration (hijra) of Muhammad and his small group of followers to Medina from Mecca and the conversion of several inhabitants of the city to Islam. The first revelation concerning the struggle against the Meccans was surah 22, verses 39-40:
To those against whom war is made, permission is given (to fight), because they are wronged;- and verily, Allah is most powerful for their aid. (They are) those who have been expelled from their homes in defiance of right,- (for no cause) except that they say, "our Lord is Allah". Did not Allah check one set of people by means of another, there would surely have been pulled down monasteries, churches, synagogues, and mosques, in which the name of Allah is commemorated in abundant measure. Allah will certainly aid those who aid his (cause);- for verily Allah is full of Strength, Exalted in Might, (able to enforce His Will). — Abdullah Yusuf Ali
This happened many times throughout history, beginning with Muhammad's battles against the polytheist Arabs including the Battle of Badr (624), and battles in Uhud (625), Khandaq (627), Mecca (630) and Hunayn (630).