How large did an army need to be to successfully storm a fortified town in the early Middle Ages? David Bachrach uses the Burghal Hidage to uncover what this remarkable document reveals about the scale of assault forces and the realities of medieval siege warfare.
By David Bachrach
It is a truism that the historian of early medieval Europe often has to work without the kinds of numerical data that those studying more modern fields take for granted. One of the most important exceptions to this general rule, however, is the document known as the Burghal Hidage. This text, which was composed during the reign of King Edward the Elder of Wessex (899-924) sometime before 914, provides details about the strengths of the garrisons in 33 fortifications (burghs) that had been established during the reign of Edward’s father, Alfred the Great (871-899). The text sets out the number of hides (measures of the value of land rather than its surface area), which were assigned to each of these fortifications to support the garrisons. On this basis, the text reads: “if every hide is represented by one man, then every pole of wall can be manned by four men. Then for twenty poles of wall, eighty hides are required.” An Anglo-Saxon pole measured approximately five meters. Thus, the military planners who drew up the Burghal Hidage document expected that four men would be required for every five meters of wall of a stronghold. All told, the document illuminates the provision of the income from 27,000 hides to support an equal number of garrison troops.
Specialists in Anglo-Saxon history generally accept the information provided in the Burghal Hidage as an accurate reflection of the military-administrative structure in the kingdom of Wessex in the early tenth century. In part, this consensus is based on understanding that the rulers of Wessex had a very thorough administrative system in place, in which government officials were able to carry out detailed inventories of the taxable land within the kingdom, and to enforce the king’s policies with regard to the mobilization of resources for military purposes.
The Burghal Hidage survives in the badly damaged manuscript Cotton Otho B.xi, although its exact folio position can no longer be determined due to the destruction caused by the 1731 Ashburnham House fire. The text is therefore known primarily through a sixteenth-century transcript made before the damage occurred. https://fragmentarium.ms/view/page/F-cfmp/726/11178
In addition, excavations of many of the fortified sites listed in the Burghal Hidage have made clear that the military planners at Edward the Elder’s court possessed very accurate information about the length of the walls of the various fortifications. At Winchester, for example, the planners assigned 2,400 hides for the support of the garrison. The walls at this old Roman fortress measured 3,034 meters. According to the formula set out in the Burghal Hidage, one would expect a garrison of 2,427 men. This represents a margin of error of just one percent. One cannot help wishing that the margin of error by modern military planners were this small!
The decision by Edward the Elder’s military advisors and planners to impose a uniform ratio of one defender for every 1.25 meters of wall despite the fact that the fortifications comprising the defensive system in Wessex varied quite significantly in size and, in some cases quality, illuminates important aspects of their tactical and strategic thinking. First, the planners do not appear to have considered the ease with which an enemy might undermine the walls of a fortification as a particularly important factor in their defense. The defenses at Winchester, for example, included a substantial subterranean element constructed in stone, whereas other strongholds built during the ninth century were constructed largely of earth and timber, and did not include substantial subterranean elements of any type. Secondly, the planners do not appear to have been concerned about the disparity in the heights of the walls. Some of these fortifications, particularly those that were Roman in origin, rose 8-10 meters above ground level. By contrast, the walls of the earth and timber burghs frequently were only half this height.
Defensive walls at the burg of Winchester – photo by Medievalists.net
In short, the planners of the Burghal Hidage garrison system appear to have concluded that their primary adversaries, that is the Vikings, lacked the technical skills that would have enabled them to bring to bear either siege engines that could overtop walls or to undermine the walls of fortifications. Rather, the main tools available to the Vikings, as seen in narrative accounts from both England and the continent, were battering rams and ladders. The one major exception to this rule was the Viking siege of Paris (885-886) when the eye-witness account by Abbo includes repeated references to the deployment of what appear to have been traction engines by the Vikings.
As a corollary, Edward the Elder’s planners appear to have assumed that the capture of any of the fortifications in the Wessex defensive system by the Vikings would have required a direct assault against the gates and walls. Under these circumstances, the Vikings would have had to cross a killing zone in which they were subject to the projectile weapons of the defenders.
Image by Hel-hama / Wikimedia Commons
As Bernard Bachrach and Rutherford Aris showed in their study of the casualties that Viking attackers likely would suffer in such an assault, the typical bow employed by Anglo-Saxon troops in this period, as identified through archaeological investigations, had a draw strength of 40-50 pounds. The maximum range of such a bow shot at a 45 degree angle was 200 meters. As the enemy closed, archers could start to pick out individual targets at about 50 meters.
Using these data and a conservative estimate of four shots per minute for archers shooting at an angle rather than picking out targets, Bachrach and Rutherford constructed a model to estimate the number of casualties that an attacking force might suffer from the time they entered the killing zone until the time they reached a point close to the walls where they no longer could be targeted by archers.
They proposed a hypothetical force of 100 defenders who began to shoot volleys of arrows when the Vikings were within 225 meters of the wall, i.e. when they were just outside the maximum effective range of the bows. Experimental data using Anglo-Saxon technology indicates that a 30 inch arrow shot from a 50 pound bow requires 6.84 seconds to travel 200 meters. Over the course of 90 seconds, these 100 archers can be understood to shoot 600 arrows. The attackers, weighed down with weapons and armor and carrying very heavy wooden ladders, would likely require close to two minutes to cover the 200 meters of the killing ground, and thus would be subject to all of these 600 arrows.
In a best case scenario for the attackers, the men in the assaulting force would spread out as uniformly as possible over as large an area as possible to reduce the risk that any individual man would be hit by a falling arrow. However, spacing out in this manner poses obvious challenges from the perspective of morale, and also would be impeded by the necessity of having groups of men carrying ladders and potentially also advancing with battering rams.
Using this best-case scenario for the attackers, however, and using probability theory regarding the likelihood that any individual arrow would strike an individual attacker, i.e. not aimed arrows but those shot an angle, Bachrach and Aris concluded that a force of 400 attackers would suffer a minimum of 100 casualties and perhaps as many as 150 casualties as they passed through the killing zone. Once the attackers were within the effective range of the Anglo-Saxon archers to take aimed shots—approximately 50 meters—and also necessarily were more closely bunched together, Bachrach and Aris estimate that they likely would have suffered a further 50 casualties.
Simply to reach the wall and before raising their ladders, the theoretical force of 400 Viking attackers can be understood to have suffered between 150-200 casualties. This level of casualties has obvious implications for the morale of the attackers. In addition, it is clear that for an attacking force that lacked sophisticated siege equipment, such as stone throwing artillery and spear casters, to have any hope of taking a fortress by storm, they required a numerical advantage of 4 to 1 or greater over the defenders.
The information regarding garrison sizes provided in the Burghal Hidage and the analysis by Bachrach and Aris regarding the likely level of casualties that Viking attackers would suffer in assaulting strongholds, which were defended by substantial numbers of archers, also have important implications for analyzing the sizes of garrisons elsewhere in contemporary Europe. In particular, whereas the deployment of one man for every 1.25 meters of wall appears to have been deemed sufficient by Edward the Elder’s military planners when dealing with Vikings, who lacked sophisticated siege equipment, it seems likely that military planners elsewhere faced the need to plan for larger garrison strengths when facing enemies who were equipped with large numbers of siege engines.
David Bachrach is a Professor at the University of New Hampshire, where he researches medieval military history, particularly in England and Germany.
How large did an army need to be to successfully storm a fortified town in the early Middle Ages? David Bachrach uses the Burghal Hidage to uncover what this remarkable document reveals about the scale of assault forces and the realities of medieval siege warfare.
By David Bachrach
It is a truism that the historian of early medieval Europe often has to work without the kinds of numerical data that those studying more modern fields take for granted. One of the most important exceptions to this general rule, however, is the document known as the Burghal Hidage. This text, which was composed during the reign of King Edward the Elder of Wessex (899-924) sometime before 914, provides details about the strengths of the garrisons in 33 fortifications (burghs) that had been established during the reign of Edward’s father, Alfred the Great (871-899). The text sets out the number of hides (measures of the value of land rather than its surface area), which were assigned to each of these fortifications to support the garrisons. On this basis, the text reads: “if every hide is represented by one man, then every pole of wall can be manned by four men. Then for twenty poles of wall, eighty hides are required.” An Anglo-Saxon pole measured approximately five meters. Thus, the military planners who drew up the Burghal Hidage document expected that four men would be required for every five meters of wall of a stronghold. All told, the document illuminates the provision of the income from 27,000 hides to support an equal number of garrison troops.
Specialists in Anglo-Saxon history generally accept the information provided in the Burghal Hidage as an accurate reflection of the military-administrative structure in the kingdom of Wessex in the early tenth century. In part, this consensus is based on understanding that the rulers of Wessex had a very thorough administrative system in place, in which government officials were able to carry out detailed inventories of the taxable land within the kingdom, and to enforce the king’s policies with regard to the mobilization of resources for military purposes.
In addition, excavations of many of the fortified sites listed in the Burghal Hidage have made clear that the military planners at Edward the Elder’s court possessed very accurate information about the length of the walls of the various fortifications. At Winchester, for example, the planners assigned 2,400 hides for the support of the garrison. The walls at this old Roman fortress measured 3,034 meters. According to the formula set out in the Burghal Hidage, one would expect a garrison of 2,427 men. This represents a margin of error of just one percent. One cannot help wishing that the margin of error by modern military planners were this small!
The decision by Edward the Elder’s military advisors and planners to impose a uniform ratio of one defender for every 1.25 meters of wall despite the fact that the fortifications comprising the defensive system in Wessex varied quite significantly in size and, in some cases quality, illuminates important aspects of their tactical and strategic thinking. First, the planners do not appear to have considered the ease with which an enemy might undermine the walls of a fortification as a particularly important factor in their defense. The defenses at Winchester, for example, included a substantial subterranean element constructed in stone, whereas other strongholds built during the ninth century were constructed largely of earth and timber, and did not include substantial subterranean elements of any type. Secondly, the planners do not appear to have been concerned about the disparity in the heights of the walls. Some of these fortifications, particularly those that were Roman in origin, rose 8-10 meters above ground level. By contrast, the walls of the earth and timber burghs frequently were only half this height.
In short, the planners of the Burghal Hidage garrison system appear to have concluded that their primary adversaries, that is the Vikings, lacked the technical skills that would have enabled them to bring to bear either siege engines that could overtop walls or to undermine the walls of fortifications. Rather, the main tools available to the Vikings, as seen in narrative accounts from both England and the continent, were battering rams and ladders. The one major exception to this rule was the Viking siege of Paris (885-886) when the eye-witness account by Abbo includes repeated references to the deployment of what appear to have been traction engines by the Vikings.
As a corollary, Edward the Elder’s planners appear to have assumed that the capture of any of the fortifications in the Wessex defensive system by the Vikings would have required a direct assault against the gates and walls. Under these circumstances, the Vikings would have had to cross a killing zone in which they were subject to the projectile weapons of the defenders.
As Bernard Bachrach and Rutherford Aris showed in their study of the casualties that Viking attackers likely would suffer in such an assault, the typical bow employed by Anglo-Saxon troops in this period, as identified through archaeological investigations, had a draw strength of 40-50 pounds. The maximum range of such a bow shot at a 45 degree angle was 200 meters. As the enemy closed, archers could start to pick out individual targets at about 50 meters.
Using these data and a conservative estimate of four shots per minute for archers shooting at an angle rather than picking out targets, Bachrach and Rutherford constructed a model to estimate the number of casualties that an attacking force might suffer from the time they entered the killing zone until the time they reached a point close to the walls where they no longer could be targeted by archers.
They proposed a hypothetical force of 100 defenders who began to shoot volleys of arrows when the Vikings were within 225 meters of the wall, i.e. when they were just outside the maximum effective range of the bows. Experimental data using Anglo-Saxon technology indicates that a 30 inch arrow shot from a 50 pound bow requires 6.84 seconds to travel 200 meters. Over the course of 90 seconds, these 100 archers can be understood to shoot 600 arrows. The attackers, weighed down with weapons and armor and carrying very heavy wooden ladders, would likely require close to two minutes to cover the 200 meters of the killing ground, and thus would be subject to all of these 600 arrows.
In a best case scenario for the attackers, the men in the assaulting force would spread out as uniformly as possible over as large an area as possible to reduce the risk that any individual man would be hit by a falling arrow. However, spacing out in this manner poses obvious challenges from the perspective of morale, and also would be impeded by the necessity of having groups of men carrying ladders and potentially also advancing with battering rams.
Using this best-case scenario for the attackers, however, and using probability theory regarding the likelihood that any individual arrow would strike an individual attacker, i.e. not aimed arrows but those shot an angle, Bachrach and Aris concluded that a force of 400 attackers would suffer a minimum of 100 casualties and perhaps as many as 150 casualties as they passed through the killing zone. Once the attackers were within the effective range of the Anglo-Saxon archers to take aimed shots—approximately 50 meters—and also necessarily were more closely bunched together, Bachrach and Aris estimate that they likely would have suffered a further 50 casualties.
Simply to reach the wall and before raising their ladders, the theoretical force of 400 Viking attackers can be understood to have suffered between 150-200 casualties. This level of casualties has obvious implications for the morale of the attackers. In addition, it is clear that for an attacking force that lacked sophisticated siege equipment, such as stone throwing artillery and spear casters, to have any hope of taking a fortress by storm, they required a numerical advantage of 4 to 1 or greater over the defenders.
The information regarding garrison sizes provided in the Burghal Hidage and the analysis by Bachrach and Aris regarding the likely level of casualties that Viking attackers would suffer in assaulting strongholds, which were defended by substantial numbers of archers, also have important implications for analyzing the sizes of garrisons elsewhere in contemporary Europe. In particular, whereas the deployment of one man for every 1.25 meters of wall appears to have been deemed sufficient by Edward the Elder’s military planners when dealing with Vikings, who lacked sophisticated siege equipment, it seems likely that military planners elsewhere faced the need to plan for larger garrison strengths when facing enemies who were equipped with large numbers of siege engines.
David Bachrach is a Professor at the University of New Hampshire, where he researches medieval military history, particularly in England and Germany.
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Further Readings:
Bernard S. Bachrach and Rutherford Aris, “Military Technology and Garrison Organization: Some Observations on Anglo-Saxon Military Thinking in Light of the Burghal Hidage,” Technology and Culture 31.1 (1990), 1-17.
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