Abstract: This study examines the development of artillery used in and around the Latin East during the period of the crusades. It begins with an examination of the broader historiography of medieval artillery, an overview of the spread of swing-beam siege engines (trebuchets) across Europe and the Levant in the Early Middle Ages, and the mechanical physics that govern such machines. From these foundations, the development and significance of the engines are investigated. Incorporating as much textual and archaeological evidence as possible, the use of artillery by Frankish and Muslim forces is examined on a case-by-case basis. With an appreciation of the power of these machines, the influence of artillery on the design of twelfth- and thirteenth-century-fortifications is analysed. Both Frankish and Muslim forces were familiar with the traction trebuchet by the end of the eleventh century. While these engines remained relatively light throughout the period of the crusades, the counterweight trebuchet appears to have been introduced by the end of the twelfth century. Initially rather primitive and little stronger than the traction variety, these engines developed fairly quickly. The appearance of new vocabulary for identifying these engines in the early thirteenth century indicates their increasing strength and physical evidence from the middle of the century confirms that they had become much more powerful by the start of the Mamluk period. Although counterweight trebuchets appear to have grown steadily throughout the thirteenth century, these had a relatively limited impact on the design of most fortifications. Trebuchets, large and small, were an important part of Frankish and Muslim siege arsenals in the twelfth and thirteenth centuries, but even the largest were not effective breaching engines by the time the Franks were pushed out of the Holy Land..