The European Crusading armies, though differing in nationality, were generally organized on much the same basis in respect to "branches". Therefore, this discussion will be divided into two main parts: cavalry and infantry, together with their respective functions as interpreted by contemporary thinkers.

The backbone of the Christian armies was the mounted knights, the heavy cavalry of its day. Armed with lance and sword, and covered with ring-metal body armor, the knight proved consistently irresistible in the charge. In the attack, the lance would be used as the main offensive weapon of the initial charge: the charge of the knights was seen as the most effective tactic of the Crusader army.

Existing alongside the knights were the lesser nobles, whose finances had not allowed them to am themselves as well as their more affluent comrades. This probably meant less body armor for the individual, but the same weaponry. They were NOT a separate sub-branch of cavalry, but, being more lightly equipped, they were occasionally called on for reconnaissance duty. However, their recognized function was no different than that of the knight heavy cavalry.

The third type of cavalry present within the Crusading armies were called Turcopoles. The main difference between them and their comrades was that they were second-generation Europeans levied from Syria. They seem to have been used for more reconnaissance-type roles than the European cavalry, and mention is also made of Turcopole mounted archers. However, like the lesser nobles, they were expected to charge with the heavy cavalry when the need arose.

Infantry

Passing on now to the infantry, we find two major subdivisions: foot soldiers and bowmen.

The former was the more numerous of the two, and ran the gamut from spear-armed pilgrim to professional, armored footmen. Most common, however, was probably the figure somewhere in between, with leanings toward the former.

The mission of the infantry was purely defensive; that is to form a solid base of maneuver for the all-important cavalry, This could be done as long as the troops stayed together and maintained a "wall of spears" attitude toward enemy cavalry charges and were supplemented by bowmen.

The bowmen, who can be further sub-divided into archers and crossbownen, had a somewhat more offensive role. The former were armed with the standard bow-and-arrow apparatus of the period, while the latter were armed with the crossbow, which fired its bolt farther, faster, and "generally more accurately than the lighter arrows of conventional archers." Though it had a slower rate of fire than the bow, its bolt was deadly due to its greater velocity.

I have said that the bowmen had a somewhat more offensive role than their infantry counterparts. In reality, they have both an offensive and defensive role; the latter, in that they were used to provide security from harassing attacks of Muslim horsearchers when the Crusading army was on the march; the former, in that a crossbow volley would be launched as a sort of ..prep bombardment" before the cavalry made its charge.

A last word on the Crusader infantry: the subdivision of foot-soldiers and bowmen was more extemporized than planned. Ideally, the infantryman was supposed to be equipped with both spear AND crossbow, not to mention body armor. More likely, this would end up as spear OR crossbow, with a heavy leather or felt jacket for protection (heavy enough, it is important to note, to stop the low-velocity Muslim arrows).

A Military History of the Third Crusade

Introduction
Jihad
Battle of Arsouf 1191
Conclusion and Bibliography
The Crusader Army
The Muslim Army
Ordnance of Siege Warfare
Crusader Kings