The second question gets us into speculative territory, as we must rely on reports of the Clermont sermon written some time later. It seems clear that he was calling for a war of liberation. This is on multiple levels. In line with the 'Peace of God' and 'Truce of God' initiatives meant to reduce feudal warfare in Europe, it could be said that one aspect of the liberation was to rescue Europe from the martial excesses of warriors by directing it outwards. In more concrete terms, it is related that he spoke explicitly of liberation of captive Christians and eastern churches, most likely intending Byzantium. Of course, by going to Byzantium's aid, the Crusade could go a great distance to healing the rift between the Catholic Church of Rome and the Orthodox Church of Constantinople going back to 1054, thus liberating the Christendom as a whole from dissent. This aspect of liberation brings us to our third question, regarding Jerusalem. When Alexius Comnenus had sent word to Urban for help, the Byzantine Emperor definitely did not have Jerusalem in mind, and there are those historians who have claimed that Jerusalem was not Urban's target either. Instead, according to this approach, Jerusalem became the goal only in the masses minds, including noble leaders as well as peasants and other aspirants. Thus, the Crusade was 'hijacked' from the beginning. Other writers do think that Jerusalem was Urban's stated goal. Jerusalem became increasingly important to eleventh-century Christians, lay and clerical alike. As well, it is possible that the political friction between Fatimids and Seljuks--along the seam of Syria and Palestine--may have made pilgrimage more difficult for Europeans. Furthermore, in charters written by people making over their goods to heirs just before departing on Crusade--and these were documents usually witnessed by clerics--Jerusalem was explicitly mentioned. The issue still remains open, but the pilgrimage aspect of the Crusades sheds some light on the matter. Urban definitely did perceive the venture as a pilgrimage of sorts, and procedures associated with a pilgrimage attended departure on Crusade--Church protection or disposition of properties left behind, the taking of avow and the wearing of the Cross, as well as the undertaking of pilgrimage-specific devotional exercises while on the trip. Thus, a pilgrimage with the ultimate goal being Jerusalem is quite plausible. In brief, then, it is likely that Urban and his cardinals envisioned an armed pilgrimage of able-bodied males to liberate Christian peoples and places, culminating with Jerusalem. Through this, Christendom as a whole would be liberated. As regards the benefit to those involved Urban is understood to have mentioned indulgence. This is a technical concept whereby the penance performed by the sinner would outweigh the punishment that would be meted out in the afterlife, and thus acquire great merit in God's eyes. In essence, the idea was that the Crusade would constitute such an arduous, dangerous undertaking that it would merit an indulgence.
What was new in all of this? Actually very little. Gregory VII, as well as Urban himself, had referred to the ongoing Reconquista as a war of liberation, and had often used terms smacking of holiness and Christian duty when referring to it. That Urban preferred Spanish knights to remain behind fighting the nearer infidel indicates that he saw the Spanish wars as analogous to a Crusade. That war could be holy was a theological idea also going back to Gregory, when his theological advisers had found in St. Augustine the notion that certain types of combat were commanded by God. Of course, the whole idea of getting knights out of Europe for domestic peace's sake was part of the reforming Church's program in terms of the 'Peace of God'. And again, liberation had always been part of the reforming plank--liberation of Christians and Christian locales abroad is not so different from liberation of Spain, or the liberation of the Church as a whole from secular rule--the aspiration from Leo IX onwards. In the same vein, the very idea that the Church could lead a military campaign is in line with the pretensions of Papal power in the temporal world, a worldly activism to improve the religion's lot. What distinguishes Urban, then, is his synthesis of ideas, and his papacy's ability to make good on them.
So much for the Papacy's take. How did the secular participants perceive it? First, it is most likely the case that on the formal level, as well as on the emotive level for several, they had similar motives as the Church's in terms of liberating Christians and Christian places. The religious frame of mind took pilgrimage and the ability to earn indulgences very seriously. At the same time, there were likely other more temporal motives. Several of the crusader leaders--not to mention the lesser knights--were 'second sons', those male members of feudal society usually left out of primogeniture-based inheritances, or given a very small portion. Going on Crusade could at the least increase the esteem in which these warriors were held back home, and at the most, they could perhaps attain their own material base--witness the creation of secular Crusader kingdoms and counties, complete with fiefs and feudal political structures. This is an important point. Rather than military administration, or even clerical administration perhaps quite appropriate to the Holy Land, the Crusader polities were reproductions of the feudal states in Europe--France, to be exact. This transplantation of a western European political system to the Middle East is one of the most intriguing aspects of crusader politics. It indicates the more worldly interests quite well. In short, on the popular level, religious motivation mixed quite thoroughly and indistinguishably with secular, mundane desires, such that while plundering merrily away in Constantinople, crusader leaders could portray and perceive their actions as religiously legitimate, even if it was a further hijacking of the Crusades.
Thus, the Crusades capture so much of the High middle Ages political, religious, and social trends. Two questions persist. How were the Crusaders able to defeat forces so much better adapted to Middle Eastern fighting, and who were the real winners of the Crusades? The first question relates to the internal political situation in the Islamic world. The Fatimids in Egypt were the confirmed enemies of the Seljuks in Anatolia and the Fertile Crescent, for political as well as religious reasons. Thus, as long as the crusading armies were passing through Seljuk lands, the Fatimids, who controlled Jerusalem at the time, were unconcerned and unwilling to take the necessary measures, even as Western armies passed through Syria. Likewise, the Seljuks were no longer concerned once the feudal host had left their domains. Thus, the political semi-vacuum of Palestine worked to Crusaders' fortune, and once they were in Fatimid lands, the Egyptian rulers a) still did not feel threatened in Cairo, and b) did not see the crusader warriors as effective militarily. It is, then no coincidence that the tide turned against the Crusades at that very juncture when Muslim leaders began to create a more unified western Islamic polity by conquering fellow Islamic statelets, from Zengi onwards. Salah al-Din al-Ayyubi was the first to restore political unity to the entire Syria-Palestine-Egypt region, and was also the Muslim leader to eject crusaders from Jerusalem. Finally, as regards the military success of the Crusades, while the Seljuks were more effective at cavalry hit-and-run, and much more mobile than the Christians, whenever the crusaders could get Muslim opponents into set battles, their heavier armor and weapons always won the day.
So, who were the real winners? The crusaders' states were ultimately totally destroyed, by the 1290s. By that time, Islamic lands were subject to Mongol invasions. But, where were the Italian maritime states? Throughout the Crusades, they used their unique role to grow commercially and politically. By the 1230s, they had bases, extraterritorial enclaves, throughout the eastern Mediterranean and Aegean, which just increased their political power as it increased the indispensability to material- and manpower-short crusader leaders. In retrospect, cities like Venice--it survived to the eighteenth century--were the real winners of the Crusades.