From 1098 to 1187, there existed in Palestine a small Frankish crusader kingdom with its capital at Jerusalem. The kingdom, surrounded by a sea of strong Muslim powers, was never of considerable strength and it never endured long enough to give rise to any sort of Frankish Syrian nationalism. Nevertheless, it was a tenacious little kingdom, jealously maintaining its tiny borders by relentless border raids and diplomatic posturing, playing rival Arab and Turkish princes off against one another in order to maintain its precarious existence. Though the Frankish Kingdom of Jerusalem was ultimately swept away by Saladin's armies after less than one hundred years, its existence had nevertheless given rise to a very unique religious culture. Unique as a Latin outpost in a Muslim east with an orthodox Christian minority, the religious culture of Frankish Syria was an eclectic mixture of contradictions: zeal and laxity, politics and religion, the highest moral ideals and the loosest of moral standards - a religious culture that was neither European, nor Muslim nor orthodox.
The fundamental point to understand when examining Frankish Syria from 1098-1187 is to distinguish between the culture of the Frankish colony of Syria and that of the the Crusading movement, whose knights and warriors continued to trickle in and out of the territory for the duration of its existence. The Franks of Syria are those who either settled in the Holy Land permanently after the First Crusade or are their descendants, men like William of Tyre, King Amalric I or Raymond III of Tripoli who were born in Frankish Syria and considered the Holy Land, not France, as their home. The Crusaders, on the other hand, refer in this article to those warriors who made temporary trips to the Holy Land in fulfillment of a vow, in penance, or in order to 'put in their time' serving with Christ's armies. These Crusaders did not view the Holy Land as their home, remained western European in thought, and ultimately left the Holy Land after a brief sojourn.
In this article we are not examining the religious ideas and motivations of the Crusaders who came and went, but rather of those first Frankish conquerors and their descendants who made Palestine their home and had to deal with the long term problems of maintaining the Frankish state amidst the sea of Muslim empires. It is important to understand this point, so that we do not assume that the aspirations and motivations of the Franks in Syria were identical with those of the Crusaders of 1095-1099.
The Frankish Attitude Towards Muslim Serfs
It has been well documented (see here) that the Crusaders and the Franks who succeeded them in Syria did not partake in forced conversions of Muslims. In fact, the Franks of Syria made very little effort to convert Muslims at all. Nevertheless, the great Muslim champion Saladin saw in the Frankish kingdom a very real threat to the integrity of the Islamic faith:
"We are convinced that if we do not find some way to take Jerusalem, and if no serious steps are taken to stamp out the religion of the infidels, it will spread its roots and become a grave threat to the true faith" .
Since it has been amply demonstrated by many historians that the Franks did not engage in any sort of systematic evangelization in Syria, either forcible or voluntary, Saladin could not have been referring to the spread of Christianity through conversion. He was in fact referring to the temporal administration of the Franks, which was superior to most contemporary Muslim princelings and atabegs. Saladin's fear was that Muslims, getting used to the relatively mild government of the Franks, would prefer Frankish rule to Muslim rule and thus would strengthen the Christian position in the East.
Saladin was not wrong in thinking this; a similar phenomenon had occurred with regard to the Greek Orthodox and the Jacobite Syrians. Because the Muslims cared little for trinitarian hair-splitting, Jacobites were treated fairly well under Muslim rule while the Greeks sought to persecute them as heretics. Thus the Jacobite Christians preferred Muslim to Greek rule, thus weakening the hand of Byzantium in northern Syria. It was not difficult to imagine a similar situation where Palestinian Muslims preferred to overlordship of the Franks to the Muslims.
Plus, Saladin was right - the Frankish treatment of their subjects was far superior to that of the Muslims. The Muslim chronicler Ibn Jubayr, who visited the Kingdom of Jerusalem in 1181, recalled the general happiness of the Muslim serfs:
"We left Tibnin on Monday at dawn by a road which ran past a series of adjoining farms, all inhabited by Moslems who live in great well-being under the Franks. The terms given to them are to yield up half their harvest at the time of reaping, and the payment of the capitation tax of one dinar and five qirats. The Christians ask nothing more, excepting only a light tax on the fruit trees, but the Moslems are the masters of their homes and run them as they like. Conditions are the same for all the rastaq, that is to say farms and small holdings inhabited by Moslems in all the territories occupied by the Franks on the coast of Syria. When they compare their situation to that of their coreligionists in cantons governed by Moslems, which is the very reverse of security and well-being, most of them are tempted by the devil. One of the misfortunes afflicting the Moslems is that under their own government they have always to complain about the injustice of those above them, while they have nothing but praise for the conduct of their enemies [the Franks] whose justice is always to be relied upon" 
The Franks were not embarking on a policy of enlightened toleration towards their Muslim subjects; they were simply transplanting Norman feudalism into Palestine, and in doing so bettered the lot of the Muslim peasants of the Holy Land. Ibn Jubayr is right in noting that the Frankish exactions were light compared to those of their coreligionists, simply because in Frankish custom they were defined by law or custom. In the Orient, it was custom for the peasants to be entirely at the mercy of the government tax collectors, who used all manner of coercion to collect as much as they could get with no legally defined limitation. Simply introducing a defined limit (and one lower than that extracted by Muslim princes at that) introduced a great deal of stability and prosperity to the agricultural economy of the Holy Land.
Of course, Ibn Jubayr mentions the capitation tax, a per head tax on non-believers; in Muslim countries, Christians were similarly taxed. But this capitation tax is probably the only real instance of a legal differentiation between Christian and infidel. The Christian royal courts made no effort to interfere in the internal life of the various communities they found already living in the Holy Land; being primarily warriors and not administrators, the first generation of Frankish conquerors decreed that each community was to obey their own leaders and be governed by their own laws in all things save military operations. In the event that two communities had a dispute, the Frankish courts acted as arbiters and the parties were made to swear by the holy books of their own religion. Even Muslim scholars of the day note the impartiality of these Frankish courts, and the Franks for their part made no legal distinction between infidels and Christians.
This was not from any love of Islam; rather, it was because the Franks had neither the time nor the means (in manpower or education) to be anything more. After 1099, when the bulk of the surviving soldiers of the First Crusade returned home, the extremely small number of the Franks made it necessary for them to be on good terms with their natives. In fact, the Franks did this much better than the Turks, who were especially hated by the Arabs, and won them the admiration and confidence of their Muslim subjects.
Latin Clergy and Ecumenism
There were greater differences between the Latin clergy and the native Christian clergy, though not as drastic as some historians have imagined. It is often supposed that the Latin Frankish clergy behaved with great arrogance towards native Greek and Jacobite clergy, considering them little better than heretics. While there was undoubtedly rivalry between the hierarchies of the various sects, it is easy to overstate their animosity.
Latin prelates enjoyed friendly relations with the heads of the Maronite Church and the Armenian Christians. Even the Jacobite Syrians, who were Monophysites, were treated well by the Latin clergy. This interesting point was noted by contemporary Jacobite historian Michael the Syrian, who noted that despite the Chalcedonian "heresy", the Franks were much preferable to the Greeks:
"Although the Franks agreed with the Greeks on the duality of the two natures of Christ, they were nevertheless very far from them in their practices. They never raised difficulties on the subject of the faith or attempted to arrive at a single form of worship for all Christian languages and peoples" 
There are several things to consider when examining the Frankish attitude to the local clergy. The Frankish clergy were certainly given pre-eminence, and naturally since the Franks were a conquering people. But it must also be remembered that at the time Jerusalem was taken, the Greek schism was only forty-five years old. Furthermore, most Latin prelates of the day regarded it as temporary and the native clergy were viewed as legitimate Christian clerics in good standing with God and Armenians, Greeks, Armenians, Maronites and Latins frequented each other's churches (the exception being the Syrian Jacobites, who regarded all the aforementioned groups as heretics and refused to worship with them). Following the taking of Jerusalem, Pope Paschal II sent the Maronite patriarch Al Jirjisi a staff affirming his authority; Innocent II reaffirmed the Maronite patriarchate in 1131. Thus, friendly relations existed between the Latins and the Eastern Churches. It seems that the canonical implications of the Greek schism had not yet been worked out; what's more, there was some doubt as to whether a formal schism even existed (see here).
Another factor is that the Latin Church of Outremer often had to rely on the "bottom of the barrel" for its prelates. There were few priests and bishops willing to uproot themselves and make the precarious passage to the Holy Land to serve the Frankish colony there; consequently, Frankish clergy had to be produced however possible, usually through nepotism or the elevation of inferior priests to ranks they never would have attained in the West. This means the Frankish clergy were not of the greatest erudition; couple this with the fact that Norman clerics of the day were not the most precise theologians; a generation earlier Cardinal Humbert of Silva-Candida had embarrassingly accused the Byzantines of "removing" the filioque clause from the Nicene Creed.
All this meant that the Frankish ruling class had neither the political will nor the requisite theological erudition to try to impose any religious uniformity on the Monophysite Syrians or the Greeks. This was especially welcome to the Armenians, Maronites and Jacobites, who were often the objects of persecution by the state Church of the Byzantine Empire. Thus, the Franks became effective protectors of these Christian minorities, and following the conquest of Jerusalem in 1099 the Frankish kingdom was swelled with Christian emigres from Armenia, Georgia and Lebanon.
The conduct of the Franks in religious matters had major ecumenical consequences. In 1140, the Armenian Catholicus Gregory III Pahlavouni entered into discussions with the Latin Church with an aim towards reunion; he carried on a friendly dialogue with Pope Innocent II and offered to revise some points of doctrine in the Armenian Church in order to facilitate reunification; this effort was stalled only by domestic political disruptions in Armenia.
A more successful episode was the formal reunion of the entire Maronite Church in 1180-1182, which was brought about largely by the efforts of the Latin patriarch of Antioch, Aimery of Limoges, who maintained the friendliest relations with Maronite patriarchs and who worked tirelessly to build positive ties with the Maronites. The Maronites have been in full communion ever since. How ironic that one of the only authentic reunifications with an Eastern Church happened in the context of the most militaristic adventures in the history of Latin Christianity!
Another example of the general atmosphere of Christian unity was the famous miracle of the Jacobite Syrian Saint Barsouma, a fourth century martyr, who in 1152 was credited with healing a sick Frankish child in Antioch. The miracle was celebrated with processions, celebrations and the dedication of a church, which was presided over by the Frankish lord Reynald of Chatillon as well as the leaders of the Syrian and Armenian churches. This same St. Barsouma was once offended by the Frankish Joscelin II of Courtenay, Count of Edessa, who plundered some monasteries dedicated to the saint. When Joscelin later fell into captivity and was blinded by his Muslim captors, he made his last confession to a Jacobite priest, but not before making full reparation to St. Barsouma.
In general, then, the Frankish clergy remained on good relations with the clergy of other churches, paying little heed to theological differences. This is not to say they did not retain a pre-eminence; they certainly did, and the Greek clergy stood the most to lose because the Franks replaced them as the dominant sect. Nor was it impossible for these native Christians to quickly turn against the Franks in cases of exploitation; the rule of Jerusalem was so incompetent during the final decades of the Frankish kingdom that the Melkite population of Jerusalem was praying for Saladin's victory in 1187. Thus, though ecumenism certainly thrived in the milieu of Frankish Syria, there was always a delicate balance to be maintained.
Latin Christianity and Islam
That balance was even more delicate when it came to religion and Islam. Although the capture of Jerusalem in 1099 had been accompanied by a frightful slaughter of its Muslim inhabitants, the Frankish armies soon realized that ill treatment of Muslims brought only further reprisals and attacks from neighboring Muslims potentates who were too numerous for the Franks to effectively defeat. Furthermore, the opposite was also true; the Franks found that Muslims were quite willing to live under Frankish rule provided things were kept tolerably quiet and they were allowed to practice their religion in peace, especially given the benefits of the Norman feudal system we have already discussed above.
This desire of keeping their Muslim subjects happy led to a level of religious tolerance unknown in the West. For example, though mosques in the Kingdom of Jerusalem were converted into churches following the conquest, it was common for the Franks to reserve a particular corner of a church for use by Muslims. Ibn Jubayr, the same chronicler who noted the happiness of Muslim peasants on Frankish lands, tells us that there was a church in Acre which had formerly been a Muslim shrine. There, a specific corner was allotted to the Muslims to pray in. Similarly, a Muslim mosque might reserve a space for use by Christians, and Ibn Jubayr mentions one of these in Acre as well. "In this way," he writes, "the Moslem and the infidel were united in this mosque, and each prayed there, turning toward the seat of his faith".
Far from dissuading Muslim prayers in Christian churches, the Frankish rulers of Syria encouraged it, knowing that nothing would rouse the Muslim population quicker than preventing them from partaking in public prayers. Once the powerful Muslim Emir of Shaizar, Usama ibn Munqidh, praying towards Mecca in a Christian church in Jerusalem, was twice bothered by a newly arrived European pilgrim who tried to forcibly turn him toward the East, telling him, "This is the proper way to pray!" He was obviously unaccustomed to the sight of Muslims praying in a church, though this was common in Frankish Syria. Some Templars who happened to be nearby warned the pilgrim to leave Usama in peace; when he refused, the Templars actually threw the offending Christian pilgrim out of the church, apologized to Usama and begged him to continue his prayers! Obviously rankled by the experience, the great emir answered that "he had prayed enough for today."  Few examples better demonstrate the affirmative position adopted by the Jerusalem Frankish elites towards local Muslims, as well as the great difference in attitude between the Franks who lived their whole lives in the Holy Land and those who only came for pilgrimage and returned home. This distinction was noted by the same Emir Usama, who in his autobiography notes, "Those of the Franks who have settled in our midst and who have frequented the society of Muslims are greatly superior to those who have come among us more recently" .
These sorts of niceties shown to Muslims were not always popular with European Catholics, nor would many traditionalist Catholics today feel comfortable with the concept of Muslims praying towards Mecca in Catholic Churches and Catholics worshiping in mosques. Medieval westerners commonly accused the Franks of Syria of being "half-Moslem" themselves, due primarily to mere externals such as the Franco-Syrian nobility's practice of wearing of silk garments, sleeping with sheets, decorating with expensive tapestries, and even wearing turbans. Yet, at a deeper level, the Franks of Syria seem to have adopted the ancient idea that Islam represented, not a different religion altogether from Christianity, but was rather more akin to a heresy, a deviation - a very profound one, but still just a distortion. Eastern Christians had long regarded Muslims as worshipers of the same God who, through the errors and perfidy of Mohammed, had been led terribly astray. They were seen as a kind of separated brethren. This was in great contrast to the Catholics of the west, who, save for the Spaniards, knew almost nothing of Islam and fancied the Muslims as worshiping a host of pagan gods, such as the Muslim trinity of Apollo, Termagant and Mahound.
Essentially, the Franks of Syria came to pay Islam a grudging respect, though from a distance. They were generally honest people, devoted to their faith, and fierce in battle, all things appreciated by the Franks. This respect for Muslims and their holy places was not absolute, however. Reynald of Chatillon, Lord of Moab, once threatened to conquer and destroy Mecca. When Saladin's armies were surrounding Jerusalem in 1187 and threatening the Franks with a frightful massacre, Balian of Ibelin, the Frankish noble who had assumed control of the city, famous stated:
"We we see that death is inevitable we shall kill our sons and our wives, we shall burn our wealth and our goods, and we shall not leave you so much as one dinar or dirhem to plunder, nor one man or woman to carry into captivity. When we have finished this work of destruction we shall tear down the Qabbat al-Sakhra and the Masjid al-Asqa and the other holy places of Islam. After that we shall slaughter the five thousand Muslim prisoners we have, and we shall slaughter all our cattle and pack animals to the last one, and then we shall come out to meet you. And thus not one of our people shall die who has not already slain several of yours."  So appreciation of Muslim religious places always gave way to the exigencies of war and the fact that, no matter what decorum was observed, Muslims and Christians members of antagonistic faiths.
Nor where Muslims incapable of appreciating Christian religious practice. We have already noted that Muslims allowed Christian worship in mosques. The same Usama ibn Munqidh, upon visiting the monastery of the Latin Christian monks of Saint John of Sebasta, Usama noted, "I witnessed there a spectacle which moved my heart, but I was saddened and pained never to have seen among Moslems a zeal such as theirs" . Though the Muslims despised the Christians as "trinitaries" and idol worshipers, they were capable of recognizing devotion when they saw it.
Frankish and Muslim Morality
Even so, the Muslims and Franks were further apart on questions of morality and society. The Muslims, for example, we appalled by the apparent freedom of Frankish women in Syria. We are familiar with Muslim attitudes towards women; what of the Syrian Franks? It is important to note that at this time (1099-1187), French society had not yet been infested with the cult of the troubadours and their concept of "courtly love." Consequently, the relations between the sexes in 12th century Norman-Frankish society were still more unrefined, almost a holdover from the time when the Norman-Franks were pagan Vikings (which was only about three or four generations back). Frankish Syrian women had an almost pagan insensitivity to the concept of shame. One Arabic writer is shocked that a Frankish nobleman allows his wife to be attended by a Muslim manservant when she is naked in her bath. Frankish ladies similarly are seen attending men with their washing, regardless of marital status. Usama tells of witnessing a Frank walking down the road with his wife when he meets another Frank, to whom he allows his wife to take arm in arm and walk with unattended! What's more, if she dallies too long, her husband will actually leave her alone with the stranger and go about his business .
So Frankish ideas of modesty and decency were not yet fully developed; this would come later with the movement towards "courtly love", which exalted women more but also secluded them more. Some historians try to link the troubadour movement and its more secluded feminine ideal to Islamic influences from Outremer, but this seems a bit tenuous.
There is so much more that could be said on this topic; what has been presented here is but a small taste. The main point, however, is to understand that the entire Crusading period ought not to be defined by the actions and zeal of 1095-1099; that, after the Franks took the Holy Land by storm in a single year in pursuit of the heavenly Jerusalem, a colony of Franks was left behind for almost a century who had to deal with the much greater problem of governing an earthly Jerusalem - and that this governance consisted in a mixture of rigid self-preservation and cultural assimilation. The Franks assimilated local culture and mores where they could, and even when they couldn't, they were more concerned with maintaining their own practices among themselves then forcing them on their subjects, whom they bent over backwards to keep happy, knowing that their hold on the kingdom was tenuous and that they were always surrounded by a sea of Muslims who could swallow their tiny kingdom at any time.
In 1187, just as that tiny kingdom was beginning to find its way and become a natural feature of the political landscape in the Holy Land, the wave the Franks had always feared rose up in the person of Saladin and washed the little crusader kingdoms off the map and into history.
 Recorded by the Arabic historian Abu Shama, who wrote a history of the reign of Saladin entitled Book of the Two Gardens, quoted in Zoe Oldenbourg, The Crusades (New York: Pantheon Books, 1966), 514.]
 Ibn Jubayr, Recueil des Historiens des Croisades: Historiens Orientaux, Vol. III, pg. 448
 Michael the Syrian, Chronicle, III
 Ibn Jubayr, Recueil des Historiens des Croisades: Historiens Orientaux, Vol. III, pg. 450-51
 Zoe Oldenbourg, The Crusades (New York: Pantheon Books, 1966), 490
 The speech of Balian is recorded in the chronicles of the Muslim scribe Ibn al-Athir, the Kamil at-Tawarikh
 H. Derenbourg, Ousama, (Paris, 1893), Vol. I pg. 189
 Oldebourg, 506]