From an early date Muslim law laid down, as one of the principal obligations of the head of the Muslim state and community, the conduct of jihãd, a term commonly, if inaccurately, translated as "Holy War." The Arabic word literally means "striving" and is often followed by the words fi sabil Allãh, "in the path of God." Until fairly recent times it was usually, though not universally, understood in a military sense. It was a Muslim duty - collective in attack, individual in defense - to fight in the war against the unbelievers. In principle, this war was to continue until all mankind either embraced Islam or submitted to the authority of the Muslim state. Until this purpose was achieved there could theoretically be no peace, though truces were permitted which in effect and duration did not greatly differ from the peace treaties that from time to time punctuated the almost continuous warfare waged by the princes of Europe against one another.
The obligation of jihad was in force on all the frontiers of Islam, beyond which lay the lands of the infidels.
Only in one area, Christendom, did Islam encounter sustained resistance, from a genuine rival faith embodied for a while in a rival polity.
This gave the jihad against Christendom a special character, for it was in these lands that Muslims saw, at different times, the greatest danger and the greatest opportunity. For the Arabs, after their conquest of Iran and central Asia and their inconclusive ventures into the borderlands of China and India, Europe was by far the most important infidel enemy. Some centuries later, for the
Ottoman Turks, there was no other.
In 710 the first Muslim raiders crossed from Morocco into Spain, invited, so it is said, by a local Spanish ruler with a grievance. By 718 they had occupied most of the peninsula and crossed the Pyrenees into France, where in 732 they encountered and were defeated by the Frankish leader Charles Martel, in the celebrated battle of Tours and Poitiers.
In Western legend and historiograhy, this is seen as the decisive victory, which turned the tide and saved Europe - Christendom - from the Saracen peril. The Arab historians, if they mention this engagement at all, present it as a minor skirmish. For them, the end of their adventure in France was due to their failure to hold the French city of Narbonne, which they first captured in 715 and finally lost in 759.
Muslim armies from Spain attacked the city and neighborhood, without success, in 793 and again as late as 840, but they did not capture it, and in time the Muslim forces withdraw south of the Pyrenees. The battle for Spain continued, and almost eight centuries passed from the first Muslim landing to the defeat and destruction of the emirate of Granada, the last Muslim state in western Europe, in 1492. This was followed, ten years later, by the first of a series of edicts giving the Muslim subjects of the Spanish crown the choice of baptism, exile, or death.
The long struggle for Spain and Portugal and the earlier struggle for southern Italy had ended in Christian victory and Muslim expulsion.
Meanwhile a new and devastating Muslim counterattack was gathering force, this time not in the west but in the east, not from the Arabs but from a new Islamic power, the Turks. Already in the eleventh century Turkish armies and migrating Turkish tribesmen had won the greater part of Anatolia from the Byzantines, transforming what had once been Greek and Christian into a Turkish and Muslim land. The eastern bastion of Christendom, which for so many centuries had withstood the Arabs, suffered the first of a series of defeats.
In time, these redrew the frontier between Christendom - Europe - and Islam.
First under the Seljuk and then under the Ottoman sultans, the Turks created one of the greatest and most enduring of the Islamic empires. In 1352 a Turkish force, brought over - like the first Arabs in Spain - as allies of a Christian contender for power, occupied the fortress of Tzympe, north of Gallipoli on the European shore of the Dardanelles.
A century later, masters of the whole Balkan Peninsula, they were ready to mount the final attack which added Constantinople, as copestone, to their new imperial structure in Europe and Asia. From their new capital in Istanbul, the Ottoman sultans launched a series of further expeditions, which brought them to the plains of Hungary and twice, in 1529 and again in 1683, to the walls of Vienna.
For a century and a half, the Turkish armies, operating from their bases in Buda and Belgrade, offered a nearer and greater threat to the heart of Christian Europe than had ever come from the Saracens in Spain. Nor was the threat limited to central and eastern Europe.
Muslim fleets, operating out of North Africa, waged naval jihad against the western European states -in the Mediterranean and even in the open seas, attacking shipping and coastal towns and villages.
In the early seventeenth century, corsairs from Algeria, now under Ottoman suzerainty, and from Morocco, were raiding the southern coasts of England and Ireland, and once -in 1627- raided as far as Iceland, where their visitation is commemorated in chronicles, sagas, and prayers.
In addition to the Moors and the Turks, there was a third Muslim advance into Europe, often overlooked by Western historians, but deeply burned into the consciousness of the East. During the thirteenth century, Mongol invaders from East Asia conquered much of Russia and eastern Europe and established a state known in Russian annals as the Khanate of the Golden Horde.
In the third quarter of the century Berke Khan, the grandson of Jengiz Khan and lord of the Golden Horde, was converted to Islam. He entered into relations with the Mamluk sultan of Egypt and began the process by which the mixed Mongol and Turkish people of his realm became a Muslim nation. They are known in eastern Europe as Tatars, after the name of one of the Mongol tribes, and the period of their domination, from the thirteenth to the fifteenth century, is known in Russian annals as "the Tatar Yoke."
after the breakup of the Khanate of the Golden Horde, the successor khanates based in Kazan, Astrakhan, and the Crimea continued to rule - and where they could not rule, to raid - parts of eastern Europe until the extinction of the last khanate, that of the Crimea, in 1783.
From 1475, the khans of the Crimea became vassals of the Ottomans. Tatar forces often fought under Ottoman command against European enemies, while Tatar raids on Russian, Polish, and Lithuanian villages provided merchandise, for centuries, for the slave markets of Istanbul.