Peter Purton

The Medieval Military Engineer: From the Roman Empire to the Sixteenth Century

(Boydell & Brewer, 2018) 365 pp. $99.00

In this excellent monograph, Peter Purton endeavors to shed new light on the important role of military engineers in medieval warfare. Rather than focus on the fairly well-known technical accomplishments of medieval architects and engineers, this study is devoted primarily to uncovering the elusive individuals who designed and produced these formidable devices, the means they used to create them, as well as the avenues by which professional knowledge was transmitted and developed by successive generations of engineers. Purton ambitiously seeks to cover technological and intellectual developments in Europe from the 5th century Roman empire up through the beginning of the 16th century, with some coverage (where relevant) of similar events in the Islamic world. Given that most medieval architects and engineers remain anonymous (given the scant explicit mention of them in most of the primary sources), this is an ambitious task, but Purton does a remarkable job of scouring chronicles, military manuals, pipe rolls, and other primary sources to try and draw as full a sketch as possible of medieval military engineers and their craft.

The book is divided into seven chapters, as well as a postscript and an appendix of engineers recorded on English pipe rolls, and the first two chapters merit special consideration in order to fully flesh out Purton’s later arguments. Purton’s first chapter provides a general survey of military engineers and engineering in the medieval period, as well as a brief overview of the relevant types of primary sources and their limitations. Purton acknowledges that, following the 5th century collapse of Roman imperial power in western Europe, there was a marked decline in the general quality of engineering available to the various Germanic successor states, but the eastern Roman empire and its Persian opponents continued to regularly employ engineers as part of their regular military operations. However, the loss of many aspects of the practical science of engineering does not mean that engineering ceased to exist; on the contrary, the continued production of structures (visible in the sources and in the archaeological record) such as bridges, walls, and ships are indicative of the fact that, while some of the finer aspects of engineering science had been lost (such as Roman pontoon bridges or the science of undermining walls), many basic foundational elements were clearly retained and practically applied in various capacities.

In chapter two, Purton continues in this vein, arguing that both the Frankish kingdom and Visigothic Spain in the west retained sufficient continuity with their Roman imperial predecessor to engage in some degree of sophisticated engineering and mechanical works, including the construction and maintenance of watermills and windmills. Purton likewise cites evidence of continuity from early medieval intellectuals, such as the 6th century Byzantine architekton Isidorus the Milesian in the east, and Isidore of Seville and Bede in the west. All these men displayed a solid grasp of classical mathematics (particularly geometry), and such mathematical knowledge found ready application in early medieval construction projects, land surveys, and – of primary interest in this volume – warfare. The evidence for such practical scientific applications of mathematical knowledge, Purton argues, can be seen in the adoption of the petrary (hand-operated trebuchet) in the Byzantine empire as a replacement for the unwieldy Roman onager in the 7th century, or Charlemagne’s use of contracted artisans to construct military bridges, canals, and fortifications, or the great fortified burhs constructed by Alfred the Great in Anglo-Saxon England. As such, while the works of early medieval military engineers may have lacked some of the technical sophistication that marked the greatest feats of Roman military engineering projects, Purton argues that the evidence from the early medieval period indicates a fair degree of continuity with intellectual knowledge and practical applications of engineering in late antiquity.

These findings challenge two popular assumptions regarding the state of early medieval science, specifically that the “Dark Age” saw little in the way of technological development, and that medieval military engineering on the whole would see no substantial technological improvements until the development of gunpowder weaponry in the 14th century. As Purton goes on to demonstrate, medieval engineers in western Europe through the ninth and eleventh centuries continued to apply their trade, both in the construction of civil and ecclesiastical structures (such as palaces, monasteries, and cathedrals) and for military purposes. By the 12th century, engineers in the west were far more closely matched with their Islamic and Byzantine contemporaries in terms of skill and knowledge, in part because of increased western contact with the east via crusading. The revival of classical learning during the 12th century “Renaissance” likewise fed an increased interest in the composition of texts that dealt with the science of engineering.

The superior coverage offered by sources from the 12th through 15th centuries – including chronicles, administrative records, and technical or scholastic treatises – makes it possible for Purton to develop a better sense of medieval engineers as people, as well as the resources and methods at their disposal during a campaign. Rather than being military professionals (as in the Roman model), medieval military engineers were typically skilled civilian craftsmen (stonemasons, carpenters, smiths, etc.) that had the practical knowledge and experience for constructing complex military fortifications or siege engines. As such, there was no meaningful distinction between civil, ecclesiastical, or military engineers in terms of vocation, and civilian artisans effectively plied their trade in all three capacities. Purton also covers – in meticulous detail – the development of increasingly complex examples of such engines as the trebuchet, as well as advances in siege mining, fortification, and gunpowder weaponry, all of which speak to the remarkable heights which medieval engineering science attained prior to the Italian Renaissance.

Purton’s knowledge of both the primary sources and the relevant scholarship is impressive. The most impressive aspect of this book is how skillfully Purton weaves together material from sources that, at first glance, do not appear to be cohesive. He gathers an impressive array of examples drawn from technical manuals, scholastic treatises on the liberal arts, pipe rolls, saints lives, and more traditional chronicle sources in an attempt to extract every relevant detail from the surviving material to support his argument. His early chapters may be faulted by some for relying to some degree on educated guesswork wherever the sources are silent or vague, but Purton is careful to ensure that all his claims are grounded as much as possible in the surviving evidence. The book is also well illustrated, with black-and-white re-prints of surviving depictions of siege engines and photographs of surviving artifacts. The Medieval Military Engineer is a superb contribution to the study of both medieval military and intellectual history, and Purton deserves high praise for his accomplished and erudite treatment of medieval engineering in warfare.

Trevor J. Davis
University of North Texas